Partitioning respiration of C3-C4 mixed communities using the natural abundance 13C approach--testing assumptions in a controlled environment.

Contributions of C3 and C4 plants to respiration of C3-C4 ecosystems can be estimated on the basis of their contrasting 13C discrimination. But accurate partitioning requires accurate measurements of the isotope signature of whole system respiratory CO2 (deltaR), and of its members (delta3 and delta4). Unfortunately, experimental determination of representative delta3 and delta4 values is virtually impossible in nature, generating a need for proxies (surrogates) of delta3 and delta4 values (e.g., the delta of leaf biomass). However, recent evidence indicates that there may be systematic differences among the delta of respiratory and biomass components. Thus, partitioning may be biased depending on the proxy. We tested a wide range of biomass- and respiration-based delta proxies for the partitioning of respiration of mixed Lolium perenne (C3) - Paspalum dilatatum (C4) stands growing at two temperatures inside large 13CO2/ 12CO2 gas exchange chambers. Proxy-based partitioning was compared with results of reference methods, including (i) the delta of whole plant respiratory CO2 (delta3 and delta4) or (ii) respiration rate of intact C3 and C4 plants. Results of the reference methods agreed near perfectly. Conversely, some proxies yielded erroneous partitioning results. Partitioning based on either the delta of shoot or root respiratory CO2 produced the worst bias, because shoot respiratory CO2 was enriched in 13C by several per thousand and root respiratory CO2 was depleted by several per thousand relative to whole plant respiratory CO2. Use of whole plant or whole shoot biomass delta gave satisfactory partitioning results under the constant conditions of the experiments, but their use in natural settings is cautioned if environmental conditions are variable and the time scales of respiration partitioning differ strongly from the residence time of C in biomass. Other biomass-based proxies with faster turnover (e.g., leaf growth zones) may be more useful in changing conditions.

The effect of age on the ovarian response to gonadotropin and on pregnancy rate in polycystic ovary syndrome.

Recent studies have proposed that, in women affected by the polycystic ovary syndrome (PCOS), aging is able to regularize the menstrual cyclicity. To evaluate the ovarian response in PCOS patients according to their age, we studied 33 PCOS patients, 20 of whom with an age ranging from 28 to 34 years (younger PCOS) and 13 ranging from 35 to 45 years (older PCOS). All patients underwent an ovulation induction therapeutic protocol with low-dose recombinant follicle stimulating hormone, for a total of 80 cycles (44 cycles for the younger PCOS group and 36 cycles for the older PCOS group). No significant difference was found between the days of therapy (12.3 +/- 5.4 vs. 13.5 +/- 5.6 days), total amount of drugs (980.7 +/- 568.9 IU vs. 1063.9 +/- 469.5 IU) or ovulation rate (93% vs. 89%) in the two groups. The two groups showed a significant difference in the maximum estradiol level (2053.5 +/- 1497.2 vs. 1269.0 +/- 911.5 pmol/l, p < 0.01), the number of the recruited and preovulatory follicles (1.7 +/- 2.5 vs. 0.64 +/- 0.9, p < 0.05 and 1.7 +/- 1.1 vs. 1.2 +/- 0.5, p < 0.01, respectively) and the pregnancy rate (36% vs. 14%, p < 0.05). In conclusion, our data clearly showed that, also in PCOS, advanced age is a negative prognostic factor in the ovarian response to ovulation induction therapies.

A pilot study of the long-term effects of acipimox in polycystic ovarian syndrome.

BACKGROUND: To evaluate the effects of long-term acipimox administration on glucose-induced insulin secretion and peripheral insulin sensitivity in polycystic ovarian syndrome (PCOS), 20 PCOS subjects (eight lean and 12 obese) and 14 body mass index-matched controls (seven lean and seven obese) were investigated. METHODS: Fasting blood samples were collected for basal hormone and lipoprotein assays, after which patients underwent an oral glucose tolerance test (OGTT). The following day a euglycaemic-hyperinsulinaemic clamp was performed. After 4-6 weeks of treatment with acipimox at a dose of 250 mg given orally three times a day, the patients repeated the study protocol. RESULTS: No significant differences were found in the glucose, insulin or C-peptide responses to OGTT before and after anti-lipolytic drug administration in any group, nor was there any effect on insulin sensitivity. Concerning the lipid profile, acipimox administration led to a significant decrease of cholesterol and low-density lipoprotein levels in obese PCOS patients as well as in obese and lean controls. Lower triglycerides were found after the drug administration in both obese groups. Post-treatment free fatty acid levels were not significantly different when compared with basal values. CONCLUSIONS: Acipimox does not appear to be an effective insulin-lowering drug in PCOS, even if it can be used in obese women with PCOS as an additional therapeutic agent to ameliorate the atherogenic lipid profile of the syndrome.

Time-domain analysis of exercise-induced ST-segment elevation in Q-wave myocardial infarction: a useful tool for the screening of myocardial viability.

BACKGROUND: Exercise-induced ST-segment elevation in Q-wave leads has been traditionally associated with passive stretching of the infarct wall, perinecrotic ischemia and, according to recent scintigraphic studies, with myocardial viability. At present, however, no definitive conclusions are available. We evaluated the potential role of a time-domain analysis of exercise-induced ST-segment elevation for the identification of viable myocardium and residual ischemia in patients with previous Q-wave myocardial infarction. METHODS: Sixty patients with a previous Q-wave myocardial infarction underwent a bicycle exercise stress test, dobutamine stress echocardiography, coronary arteriography and left ventriculography. RESULTS: Patients with exercise-induced ST-segment elevation in Q-wave leads (n = 36) showed more severe impairment of resting left ventricular function, when evaluated in terms of wall motion score index at echocardiography (1.62 +/- 0.33 vs 1.41 +/- 0.22, p < 0.01) and in terms of wall motion score at ventriculography (5.9 +/- 1.6 vs 4.1 +/- 1.5, p < 0.03), compared to patients without ST-segment shift (n = 24). No differences between the two groups were seen in the severity and extension of coronary artery disease. The two groups of patients did not differ in the overall incidence of viability (50% in patients with vs 62% in those without ST-segment elevation, p = NS) and homozonal ischemia (39 vs 26%, p = NS), when evaluated with dobutamine echocardiography. However, a time-domain analysis of the ST-segment changes during exercise showed that the duration of exercise up to 0.1 mV ST-segment elevation was significantly lower in patients with viability (6.2 +/- 3.3 min) than in those without (10.2 +/- 2.2 min) (p < 0.001). Accordingly, ST-segment elevation occurred within 3 and 6 min of exercise in 7/18 and in 12/18 patients with viability respectively, but in only 0/18 (p < 0.01) and in 1/18 (p < 0.01) patients without viability. Thus, ST-segment elevation occurring within the first two stages of the exercise test was, respectively, 39 and 67% sensitive and 100 and 94% specific for viability. Early onset ST-segment elevation (within 3 and 6 min) was also more frequent in patients with high-dose dobutamine-induced homozonal ischemia than in those without (sensitivity for ischemia 50 and 67%; specificity 95 and 74%, respectively). CONCLUSIONS: After myocardial infarction, ST-segment elevation in Q-wave leads at the peak of exercise is associated with severe resting left ventricular dysfunction but fails to identify patients with a viable myocardium or residual ischemia. Instead, ST-segment elevation occurring in the early phases of exercise is a highly specific, although not very sensitive marker of dobutamine-assessed viability in the infarct area and may be indicative of residual ischemia.

Torsional Splitting in the nu(5) Fundamental Infrared Band of CH(3)CD(3) and (13)CH(3)CD(3).

The nu(5) fundamental (C-C stretching) of CH(3)CD(3) shows a resolved torsional structure, caused by perturbations due mainly to the linear dependence of the torsional potential barrier on the normal coordinate Q(5). We were able to analyze this structure and to assign vibration-rotation transition wavenumbers for all five torsional components, classified according to the symmetry species of the G(18)((3)) extended molecular group. The torsional splitting pattern is qualitatively similar to that of a nondegenerate vibrational state with an even number of excited torsional quanta v(6). Explorative calculations show that the main perturber system should consist of the torsional components of the vibrational ground state correlating with v(6)=4 in the high barrier limit. The strength of the perturbation on the E(r0) torsional components of nu(5) increases rapidly with r, the E(40) component being the most affected. The observed transition wavenumbers can be reasonably fitted by a simplified model containing independent effective vibration-rotation parameters for the five different torsional components of nu(5), for both CH(3)CD(3) and (13)CH(3)CD(3). The trend of the determined values of the effective vibrational wavenumbers and rotational parameters over the torsional components supports the proposed vibration-torsion interaction mechanism, responsible for the observed torsional splittings. A strong anomaly observed in the rotational intensity distribution of nu(5) is discussed. Copyright 2001 Academic Press.

Prognostic value of pharmacologic stress echocardiography in patients with left bundle branch block.

PURPOSE: Although coronary artery disease is a frequent cause of left bundle branch block, the prognostic value of myocardial ischemia in patients with this conduction abnormality has not been defined. We investigated the value of pharmacologic stress echocardiography in risk stratification of patients with left bundle branch block. PATIENTS AND METHODS: Three hundred eighty-seven patients [230 men and 157 women, mean (+/- SD) age, 64 +/- 9 years] with complete left bundle branch block on the resting electrocardiogram underwent dobutamine (n = 217) or dipyridamole (n = 170) stress echocardiography to evaluate suspected or known coronary artery disease. A summary wall motion score (on a one to four scale) was calculated. The primary end points were cardiac death and nonfatal myocardial infarction. RESULTS: A positive echocardiographic result (evidence of ischemia) was detected in 109 (28%) patients. During a mean follow-up of 29 +/- 26 months, there were 21 cardiac deaths and 20 myocardial infarctions, 63 patients underwent coronary revascularization, and 1 patient received a heart transplant. In a multivariate analysis, four clinical and echocardiographic variables were associated with increased risk of cardiac death: resting wall motion score index [hazard ratio (HR) = 7.5 per unit; 95% confidence interval (CI), 2.8 to 20; P = 0.001], previous myocardial infarction (HR = 2.9; 95% CI, 1.1 to 7.3; P = 0.02), diabetes (HR = 2.7; 95% CI, 1.1 to 6.6; P = 0.03), and the change in wall motion score index from rest to peak stress (HR = 3.0 per unit; 95% CI, 1.0 to 8.6; P = 0.04). The 5-year survival was 77% in the ischemic group and 92% in the nonischemic group (P = 0.02). Four variables were associated with increased risk of cardiac death or infarction: previous myocardial infarction (HR = 3.4; 95% CI, 1.7 to 6.8; P = 0.0005), diabetes (HR = 2.4; 95% CI, 1.2 to 4.6; P = 0.01), resting wall motion score index (HR = 2.2 per unit; 95% CI, 1.1 to 4.1; P = 0.02), and positive echocardiographic result (HR = 2.2; 95% CI, 1.1 to 4.5; P = 0.03). The 5-year infarction-free survival was 60% in the ischemic group and 87% in the nonischemic group (P < 0.0001). Stress echocardiography significantly improved risk stratification in patients without previous myocardial infarction (P = 0.0001), but not in those with previous myocardial infarction (P = 0.08). In particular, it provided additional value over clinical and resting echocardiographic findings in predicting cardiac events among patients without previous infarction. CONCLUSIONS: Myocardial ischemia during pharmacologic stress echocardiography is a strong prognostic predictor in patients with left bundle branch block, particularly in those without previous myocardial infarction.

Torsional Splitting in the Degenerate Vibrational States of (70)Ge(2)H(6): Rotation-Torsion Analysis of the nu(7) and nu(9) Fundamentals.

The rotational and torsional structure of the nu(7) and nu(9) degenerate fundamentals of (70)Ge(2)H(6) has been analyzed under high resolution. The torsional structure of both v(7) = 1 and v(9) = 1 states can be fitted by a simple one-parameter formula. The x,y-Coriolis interaction with the parallel nu(5) fundamental was accounted for in the analysis of nu(7). A strong perturbation of the J structure of the E(3s) torsional component of the KDeltaK = -2 subbranches of nu(9) can be explained by the resonance with an E(3s) excited level of the pure torsional manifold. The perturber is centered at 361.58 cm(-1), very close to the value estimated with a barrier height of 285 cm(-1). This confirms that the fundamental torsional wavenumber is close to 103 cm(-1), in good agreement with the "ab initio" prediction. The torsional splittings of all the infrared active degenerate fundamentals, nu(7), nu(8), and nu(9), follow the trend predicted by theory, and have been fitted by exploratory calculations accounting only for the torsional Coriolis-coupling mechanism of all degenerate vibrational fundamentals in several torsional states. This confirms that torsional Coriolis coupling is the dominant mechanism responsible for the decrease of the torsional splitting in the degenerate vibrational states. A higher value of the barrier had to be used for the nu(9) mode. Copyright 2000 Academic Press.

Dobutamine stress echocardiography: safety in diagnosing coronary artery disease.

Dobutamine stress echocardiography is considered a relatively well-tolerated diagnostic modality, effective in the management of patients with known or suspected coronary artery disease. Adverse effects during testing are relatively frequent, precluding the achievement of a diagnostic end-point in about 5 to 10% of tests. These adverse effects, mostly tachyarrhythmias and arterial hypotension, are usually minor and self limiting. However, severe life-threatening complications, as well as death, also occur. By analysing Medline-quoted literature up to March 1999, we found 35 original studies from a single institution with more than 100 patients, as well as 2 multicentre studies, concerning the feasibility and safety of dobutamine stress echocardiography. In a cumulative total of 26438 tests performed, 79 life-threatening complications (such as acute myocardial infarction, asystole, ventricular fibrillation, sustained ventricular tachycardia or severe symptomatic hypotension) have been reported, giving an incidence of 1 severe adverse reaction per every 335 examinations. In addition, 29 isolated case reports have been published describing life-threatening complications during dobutamine echocardiography. In case reports, 2 deaths have been described, both due to acute cardiac rupture in patients with recent inferior myocardial infarction. Severe adverse reactions during dobutamine echocardiography can be ischaemia independent, and are independent of operator experience and are unpredictable; some complications can be late occurring and long lasting. As a consequence, the procedure must be clearly indicated, written informed consent has to be obtained from the patient, an attending physician must be present during testing, and long term observation of outpatients is useful in order to manage late complications. In conclusion, while the safety of dobutamine stress echocardiography was reported to be outstanding in early reports, further experience presents a substantially more worrying picture. This must be taken into account by both physicians and patients when assessing the risk-benefit profile of the procedure.

Head and Tail Deformations, Torsional Coriolis Coupling, and E(1d)-E(2d) Vibrational Mixing in Ethane-Like Molecules.

The mechanism of torsional Coriolis interaction of E(1d) and E(2d) vibrational modes in ethane-like molecules is investigated, and it is shown that this coupling can drastically affect the torsional splitting in the degenerate vibrational states. A basic point of our treatment is that the sets of coordinates of head and tail which combine with the + sign to generate E(1d) normal coordinates are in general different from those which combine with the - sign to generate E(2d) normal coordinates. It is shown that the zeta(gamma) torsional Coriolis coefficients calculated by the usual methods of normal mode analysis are related to the vibrational angular momenta within head and tail referred to the internal rotor axis systems. With knowledge of the L and L(-1) matrices it is possible to transform these coefficients for reference to the molecule-fixed frame. It is peculiar that torsional Coriolis matrix elements occur between E(1d) and E(2d) vibrational components with the same x or y orientation in the molecule-fixed frame. The matrix elements of the torsional Coriolis operator and other operators responsible for the end-to-end coupling are determined, and a method for calculating vibration-torsion energies, and then torsional splittings, in degenerate vibrational states is outlined. Detailed calculations require a global model, involving all the degenerate vibrational basis states in a complex mechanism of interactions, but it is shown that useful information can be obtained by means of simplified models. Our semiempirical rule that degenerate vibrational states with a large negative value of the diagonal vibration-rotation Coriolis coefficient are likely to deviate much from the behavior of E(1d) or E(2d) vibrational states, with a sensible decrease of the torsional splittings, is confirmed. Copyright 1999 Academic Press.

Rotation-Torsion Analysis of the High-Resolution nu(6) and nu(8) Fundamentals of (70)Ge(2)H(6).

The nu(6) (A(4s)) and nu(8) (E(1d)) Coriolis coupled fundamental bands of (70)Ge(2)H(6), occurring between 730 and 950 cm(-1), have been rotationally analyzed under high resolution. The interactions of nu(8) with the nearby lying nu(2) + nu(4) (A(4s)), 2nu(3) + nu(9) (E(1d)), and nu(-/+1)(9) + nu(-/+1)(12) (E) have also been accounted for in the analysis. We determined rotational constants of the ground state, vibrational and rotational parameters of nu(6) and nu(8), interaction parameters, and a few leading parameters of the other three mentioned perturbers of nu(8). The torsional barrier height is estimated about 285 cm(-1), leading to the prediction of a tunneling splitting of about 0.049 cm(-1) in the ground torsional state. No torsional splitting was observed in the nu(6) band, showing that the splittings in the v(6) = 1 vibrational state are the same as in the ground state. The nu(8) band shows almost constant splittings of about 0.047 cm(-1). This result and the assignments of the split torsional components in all the observed subbranches of nu(8) show that the torsional splittings in the v(8) = 1 state are quite small, and the observed splittings are almost completely due to the ground state. We have proved by numerical calculation that the lowering of the torsional splitting found in the v(8) = 1 state can be explained by the vibration-torsion (gamma-Coriolis) coupling mechanism of the degenerate vibrational states. Copyright 1999 Academic Press.

Protective effect of nisoldipine on dipyridamole-induced myocardial ischemia: correlation with exercise electrocardiography.

BACKGROUND: Nisoldipine, a dihydropyridine calcium channel blocker with strong coronary dilatative action, is commonly used in the treatment of myocardial ischaemia; its beneficial effect on effort angina has been demonstrated by several previous reports. Infusion of dipyridamole in doses sufficient to provoke myocardial ischaemia in patients with significant coronary artery disease is used safely in imaging studies for diagnostic purposes. OBJECTIVE: To evaluate the potential effect of nisoldipine on dipyridamole-induced ischaemia and to compare the results with the effect of nisoldipine on exercise-induced ischaemia. METHOD: Twelve patients (10 men and two women, mean age 62 +/- 8 years) with significant coronary artery disease (at least 70% lumen reduction in at least one major coronary vessel) were selected for inclusion in the study. In accordance with the inclusion criteria, the patients exhibited an ischaemic diagnostic response to a multistage exercise electrocardiography stress test (> 0.15 mV ST segment depression compared with the resting electrocardiographic tracing) and to a dipyridamole-echocardiography test (transient left ventricular dyssynergy of contraction during infusion of dipyridamole up to 0.84 mg/kg over 10 min), after 3 days' cessation of antianginal treatment. After treatment with oral nisoldipine (10 mg twice daily) was introduced, the patients repeated the two tests, within 18 days of the first evaluation. RESULTS: The dipyridamole-echocardiography test was positive for ischaemia in 12 patients who were not receiving nisoldipine and in eight patients who were receiving the drug (100% and 67% respectively, P < 0.05). In the eight patients who gave positive dipyridamole-echocardiography tests both with and without treatment, dipyridamole time (time to onset of dyssynergy during the test) increased from 7.9 +/- 2.9 min to 10.2 +/- 3.1 min (P < 0.01). In these patients, no significant changes were observed, at ischaemia, in the severity and extent of induced dyssynergy, evaluated as wall motion score index (each of 16 left ventricular segments scored from 1 = normal to 4 = dyskinetic) after treatment (score variations from baseline to ischaemia: 0.20 +/- 0.11 without nisoldipine and 0.16 +/- 0.06 with nisoldipine; NS). Variations in dipyridamole time (arbitrarily considered to be 15 min in the negative dipyridamole-echocardiography test) were significantly correlated with variations in exercise time (duration of exercise to exhaustion or diagnostic positive response on the electrocardiogram): r = 0.75 (P < 0.01). No significant differences were recorded in rate-pressure product (beats/min x mmHg x 100) at peak ischaemia between patients who were or were not receiving nisoldipine, during either the exercise electrocardiography stress test (233 +/- 36 with nisoldipine and 244 +/- 39 without nisoldipine; NS) or the dipyridamole-echocardiography test (147 +/- 21 with nisoldipine and 133 +/- 30 without nisoldipine; NS). CONCLUSION: Nisoldipine treatment can protect from dipyridamole-induced ischaemia, being associated with a longer stress time, and completely preventing the development of ischaemia in some patients. The therapy-induced changes in ischaemic threshold during the dipyridamole-echocardiography test correlate with variations in exercise tolerance.

Hyperkinetic ventricular arrhythmias in very elderly people with and without cardiac disease. Correlation with left ventricular echocardiographic parameters.

BACKGROUND: Morphological and functional changes induced by aging can hamper a clear distinction between pathological or paraphysiological phenomena in very old people. The incidence of hyperkinetic ventricular arrhythmias, for example, progressively increases in the elderly, even in the absence of overt cardiac disease. METHODS: One-hundred fifty-two clinically stable patients older than 80 years, submitted within 15 days to clinical evaluation, 24-hour continuous ambulatory ECG monitoring and echo Doppler examination, in the absence of antiarrhythmic treatment, were retrospectively selected in order to evaluate the incidence of ventricular arrhythmias, in patients with and without significant heart disease. The further aim of the study was to correlate the number of arrhythmias with left ventricular morphological and functional parameters, echocardiographically assessed. From the initial population, 80 patients (41 males, age 83 +/- 3 years) had significant heart disease (ischemic, hypertensive or valvular): Group I. Seventy-two patients (30 males, age 83 +/- 3 years) had no clinical or instrumental signs of heart disease: Group II. RESULTS: Considering echocardiographic data, Group I patients had a significantly higher left ventricular end-diastolic diameter (52 +/- 6 mm vs 47 +/- 4 mm, p < 0.01), lower ejection fraction (57 +/- 10% vs 64 +/- 6%, p < 0.01) and higher mass (275 +/- 84 g vs 208 +/- 46 g, p < 0.01), when compared with Group II. From ECG monitoring data, significant differences between the two groups were recorded in the incidence of premature ventricular beats per hour (79 +/- 163 vs 15 +/- 34, Group I vs Group II, p < 0.01) and presence of complex phenomena (couplets, triplets and runs: 51% vs 22%, p < 0.01). In old patients with documented cardiac disease a significant correlation was present between premature ventricular beats incidence and left ventricular end diastolic diameter (r = 0.39, p < 0.05) and left ventricular ejection fraction (r = 0.40, p < 0.05), while in patients without heart disease, no significant correlation was found between incidence of premature ventricular beats and echocardiographic morpho-functional parameters. CONCLUSIONS: In conclusion, hyperkinetic ventricular arrhythmias are globally frequent in old persons of very advanced age (more than 80 years), but, also in this subset, a significant distinction in terms of incidence and severity of arrhythmias is present between subjects with and without cardiac disease. A significant correlation between incidence of premature beats and non-invasive morpho-functional left ventricular parameters is present only for patients with overt heart disease.

Role of stress echocardiography in risk stratification early after an acute myocardial infarction. EPIC (Echo Persantin International Cooperative) and EDIC (Echo Dobutamine International Cooperative) Study Groups.

Resting and stress echocardiography is a 'one-stop shop', which enables a wide range of information to be collected on resting function, myocardial viability, and induced ischaemia, all of which are useful for prognostic stratification. Large scale, multicentre, prospectively collected data show the prognostic failure of resting function and inducible ischaemia, both independently and combined, which are especially effective in predicting cardiac death. The GISSI data show that the increment of risk as a result of reduction in ventricular function has a hyperbolic trend, with a relatively moderate increase in mortality for ejection fraction values between 50 and 30%, but with marked increases below 30%. The EPIC data show that the 1-year risk of cardiac death is as low as 2% in patients with negative dipyridamole stress echocardiography: it doubles if the test is positive at a high dose, and is almost four times higher if it is positive at a low dose. In the field of prognostic stratification, in the absence of carefully controlled studies, the choice between coronary angiography as the only essential study, or use of a non-invasive test to discriminate access to catheterization currently reflect alternate philosophical approaches rather than scientifically based decisions. In the invasive approach, stress echocardiography offers relief from the vicious circle of chest pain-coronary angiography revascularization. In the non-invasive and physiological approach, stress echo is capable of offering, in one sitting, an insight into the main determinants of survival: function, viability, and ischaemia.

[Measurement of cardiac output with continuous thermodilution. b1 Clinical experience with the Intellicath-Vigilans system]. / Gittata cardiaca misurata mediante termodiluizione continua. Esperienza clinica con il sistema Intellicath-Vigilans.

BACKGROUND: Thermodilution cardiac output measurements are commonly obtained by a manual bolus technique with a pulmonary artery catheter. METHODS: A new thermodilution catheter has been developed which utilizes an integral thermal filament and provides semicontinuous online cardiac output. The response of this new device in 25 patients undergoing coronary artery bypass grafting was examined. A total of 250 data pairs was obtained; the cardiac outputs ranged from 2.2 to 11.9 lts.min. RESULTS: The linear regression is represented by the following equation: continuous thermodilution = 0.7196 bolus thermodilution +1.038. The correlation coefficient was 0.75; the mean bias was 0.493 +/- 1.034. CONCLUSIONS: The new technique provides acceptable accuracy in many clinical situations except when sudden haemodynamic changes occur.

[Left atrial myxoma evidenced by silent acute myocardial infarction]. / Myxoma atriale sinistro manifestatosi con infarto del miocardio acuto silente.

A 64-year-old female patient was in-hospital admitted due to a traumatic femoral fracture. A routinely performed ECG showed signs of anterior acute myocardial infarction, clinically silent, and pathological levels of myocardial serum enzyme were recorded. The echocardiographic-Doppler examination confirmed the LV dyssynergy of contraction and, unexpectedly, revealed a large peduncolated and mobile mass in left atrium, connected to the interatrial septum and prolapsing in left ventricle, referable to myxoma. In the clinical history of the patient, a previous cerebral transitory ischemic attack was present (probably due to myxomatous embolization), but no any other cardiovascular symptoms. The patient successfully underwent coronary angiography, which showed no coronary artery disease, and cardiac surgery for tumoral removal. On the basis of clinical and instrumental data, also acute myocardial infarction may be considered a very likely consequence of a intracoronary embolus. Systemic embolization from left atrial myxomas are frequent; however, the involvement of coronary tree, with clinical manifestations and diagnosis during life, is extremely rare. Complete lack of symptoms due to atrial myxoma and myocardial infarction, and the fortuitous diagnosis of both diseases are peculiar findings of the reported case. Many systemic embolizations from myxomas, although sources of tissue damages, may likely occur without symptoms and may be unrecognized during acute period.

[Propafenone and flecainide in the therapy of ventricular arrhythmias]. / Il propafenone e la flecainide nella terapia delle aritmie ventricolari.

Flecainide and propafenone are antiarrhythmic drugs of the class 1C (Vaughan and Williams) commonly used for ventricular arrhythmias. The purpose of the present study was to evaluate the efficacy of these drugs in 170 consecutive patients with ventricular arrhythmias who referred to our cardiological ambulatory. The study population was divided into two groups according to the absence (group A,82 patients) or presence of organic heart disease (group 1B: 51 patients with left ventricular ejection fraction (LVEF) >35%; group 2B: 37 patients with LVEF<35%). Ventricular arrhythmias were evaluated with a 48 hours Holter monitoring at baseline, and with a control 24 hours Holter monitoring at 15 days (for optimizing the dosage), at 5 months and at 10 months from the beginning of antiarrhythmic therapy. Patients of group A were randomly assigned to antiarrhythmic treatment (flecainide 150-300 mg/die or propafenone 450-900 mg/die). For patients of group B, such choice was leaded by the clinical and strumental data (32 patients were treated with flecainide, 56 patients with propafenone). In the 160 patients who ended the 10 months follow-up, we observed the following results: patients of group A showed a mean percentage reduction in incidence of premature ventricular complexes (PVC) after therapy in comparison to basal conditions of 93% and 89% with flecainide and propafenone, respectively, after a treatment of 5 months (p < 0.001); after 10 months mean percentage reduction of PVC was 91% with each drug (p = n.s.); complex ventricular events (CVE) were reduced of 90% and of 100% after 5 and 10 months, respectively, of treatment with flecainide and of 100% both after 5 and 10 months of treatment with propafenone (p = n.s.) -- patients of group 1B showed a mean percentage reduction of PVC of 87% and 84% after 5 and 10 months, respectiively, of treatment with propafenone (p = n.s.); after 5 months of therapy mean percentage CVE reduction was 66% with flecainide and 86% with propafenone (p < 0.001); after 10 months this mean reduction was 53% with flecainide and 73% with propafenone (p < 0.001). -- patients of group 2B showed a mean reduction of PVC of 59% and 58% after 5 and 10 months of therapy with flecainide, and of 65% and 67% after 5 and 10 months of therapy with propafenone (p = n.s.); CVE were reduced of 28% with flecainide and of 47% with propafenone after 5 months of treatment (p < 0.001) and of 36% with flecainide against 52% with propafenone after 10 months (p < 0.01). In the present study there was no significant difference between the two drugs in terms of tollerance and collateral effects (8% with flecainide vs 7%, with propafenone). Our results confirm the efficacy of the 1C class drugs in the treatment of "essential" ventricular arrhytmias. This efficacy appears reduced in non selected patients with organic heart disease. In these latter patients propafenone has shown more efficacy than flecainide in reducing CVE.

Diagnostic and prognostic value of dipyridamole echocardiography in patients with suspected coronary artery disease. Comparison with exercise electrocardiography.

BACKGROUND: Before any new diagnostic test is accepted in clinical practice, such a test should be compared with established diagnostic tools in an appropriately large series of patients encompassing the complete spectrum of challenges to which the test is exposed. The aim of the present study was to assess the relative diagnostic and prognostic accuracies of high-dose dipyridamole echocardiography (two-dimensional echocardiographic monitoring during dipyridamole infusion up to 0.84 mg/kg over 10 hours) versus maximal symptom-limited bicycle exercise ECG test in patients with angina. METHODS AND RESULTS: We studied 429 consecutive in-hospital patients who met the following inclusion criteria: history of chest pain, off antianginal therapy for at least 2 days (1 week for beta-blockers), no previous myocardial infarction and/or obvious regional left ventricular dyssynergy of contraction (akinesis or dyskinesis) at baseline, and acceptable acoustic window under resting conditions. All patients underwent dipyridamole echocardiography and exercise ECG--on different days and in random order--within 1 week of coronary angiography (which was performed independent of test results) and were followed up for 37.8 +/- 14 months (range, 1 to 73 months). Criteria of positivity were for dipyridamole echocardiography, a transient regional dyssynergy absent in the baseline examination; for exercise ECG, an ST-segment shift of > or = 0.1 mV from baseline; and for coronary angiography, a luminal reduction of > or = 75% in at least one major coronary vessel (50% for left main). There were 183 patients without and 246 with coronary artery disease; 132 had one-, 70 had two-, and 44 had three- and/or left main vessel disease. The specificity was higher for dipyridamole echocardiography than for exercise ECG (90% versus 51%, P < .001). The overall sensitivity of dipyridamole echocardiography was similar to that of exercise ECG (75% versus 74%, P = NS), with no significant differences in the subset with one- (67% versus 69%, P = NS), two- (79% versus 77%, P = NS), or three- (93% versus 86%, P = NS) vessel disease. During the follow-up, there were 20 deaths, 13 nonfatal myocardial infarctions, and 126 revascularization procedures. In the univariate analysis, dipyridamole resulted in higher chi 2 values than did exercise stress testing. A Cox forward stepwise survival analysis identified the dipyridamole time as the most powerful prognostic predictor of death (chi 2 = 19.4, P < .0001) of all invasive and noninvasive parameters. The dipyridamole time also provided independent and additional prognostic information when it was adjusted for age, diabetes, resting ECG, and exercise stress test according to a modified, interactive stepwise procedure. This is true when death only, death and myocardial infarction, and death, myocardial infarction, and revascularization procedures were considered end points. CONCLUSIONS: In patients with no previous myocardial infarction and good resting left ventricular function, compared with exercise ECG, dipyridamole echocardiography has a similar sensitivity and a higher specificity for the noninvasive detection of angiographically assessed coronary artery disease. Dipyridamole echocardiography also provides information in addition to that provided by exercise ECG for predicting death, infarction, and all events when the presence as well as the timing, severity, and extension of dipyridamole-induced wall motion abnormalities are considered.

Assessment of anatomic and physiological severity of single-vessel coronary artery lesions by dipyridamole echocardiography. Comparison with positron emission tomography and quantitative arteriography.

BACKGROUND: The aim of this study was to compare the results of dipyridamole-echocardiography test (DET: two-dimensional echo monitoring during dipyridamole infusion up to 0.84 mg/kg over a period of 10 minutes) with both anatomic and physiological parameters of coronary artery disease severity, assessed by computer-assisted quantitative coronary arteriography, and regional coronary flow reserve, measured by [13N]ammonia (13NH3) and dynamic positron emission tomography (PET), respectively. METHODS AND RESULTS: We studied 31 patients with a history of chest pain and neither previous myocardial infarction nor resting wall motion abnormalities. Eighteen patients had single-vessel disease (> 50% stenosis of one major coronary vessel), and 13 had normal coronary arteries. The criterion for DET positivity was the appearance of a new transient regional wall motion abnormality. In patients with a positive DET, two parameters were evaluated: the dipyridamole time (ie, the time from the beginning of drug infusion to the development of obvious dyssynergy) and the wall motion score index (WMSI, a semiquantitative integrated estimation of extent and severity of the stress-induced dyssynergy). WMSI was derived by summation of individual segment scores divided by the number of segments interpreted. Quantification of regional myocardial blood flow was obtained by PET measurements of 13NH3 arterial input function and left ventricular myocardial tissue concentration both at control and after dipyridamole (0.56 mg/kg over 4 minutes). Maximal regional blood flow after dipyridamole in the region supplied by the stenotic vessel was significantly lower in the 11 patients with coronary artery disease and positive DET than in the 7 patients with coronary artery disease and negative DET (1.08 +/- 0.33 versus 1.98 +/- 0.37 mL.min-1.g-1, P < .01). In patients with a positive DET, regional coronary flow reserve correlated well with dipyridamole time (r = .87, P < .01) but not with peak WMSI (r = .25, P = NS). Patients with dipyridamole-induced akinesia or dyskinesia (n = 6) had a greater reduction in regional coronary flow reserve than did those showing hypokinesia (n = 5): 1.38 +/- 0.51 versus 2.17 +/- 0.42, P < .05. Percent area reduction was more severe in patients with DET positivity than in those with DET negativity (93.7 +/- 8.7% versus 77 +/- 10.3%, P < .01), and it correlated with regional coronary flow reserve (r = .64, P < .01) and dipyridamole time (r = -.59, P < .01). CONCLUSIONS: In patients with single-vessel disease, DET shows an excellent specificity but a limited sensitivity; in these patients, DET positivity is associated with a physiologically important coronary stenosis. Severity of the anatomic stenosis and impairment in regional flow reserve are greater when the dipyridamole-induced dyssynergy appears earlier during the test. Therefore, a stratification of the anatomo-physiological severity of coronary artery disease can be obtained with DET, based mainly on the temporal allocation of the transient dyssynergy.

Regression of hypertensive myocardial hypertrophy does not affect ultrasonic myocardial reflectivity: a tissue characterization study.

OBJECTIVE: Ultrasonic backscatter from the myocardial walls is directly related to the morphometrically or biochemically evaluated collagen content in man, and shows a normal pattern of quantitatively assessed ultrasonic backscatter in hypertensive patients, even in the presence of left ventricular hypertrophy. Whether the pharmacologically induced regression of left ventricular hypertrophy in hypertensive patients is accompanied by a disproportionate increase in relative connective tissue content is not yet known. The objective of the present study was to assess the effects of regression of left ventricular hypertrophy on the quantitatively evaluated myocardial reflectivity in essential hypertensives. DESIGN: We evaluated 19 mild-to-moderate essential hypertensives with echocardiographically assessed left ventricular hypertrophy, before and after 8 months' effective antihypertensive therapy with 20-40 mg enalapril once a day, associated with diuretics or calcium antagonists, or both, in six patients to achieve optimal blood pressure control. Using a modified echo machine developed in the Institute of Clinical Physiology, Pisa, an on-line radio-frequency analysis was performed to obtain quantitative operator-independent measurements of the integrated backscatter signal of the ventricular septum and the posterior wall. The integrated values of the radio-frequency signal from the myocardial walls were normalized for those from the pericardial interface and were expressed as percentages (integrated backscatter index). RESULTS: In comparison with baseline, the treated hypertensives showed significant decreases in mean blood pressure, left ventricular mass index, and septal and posterior wall thickness. However, integrated backscatter index values were similar at baseline and after therapy for both the septum and the posterior wall. CONCLUSION: Antihypertensive therapy with enalapril does not increase myocardial reflectivity, although it does induce regression of left ventricular hypertrophy. This suggests that, in accord with experimental data, regression of hypertrophy is achieved by enalapril through a proportionate regression of the myocyte and connective tissue components of the myocardium.

[The ultrasonic characterization of myocardial hypertrophy: new prospects]. / Caratterizzazione ultrasonica della ipertrofia miocardica: nuove prospettive.

The extensive use of ultrasound imaging in cardiology has greatly contributed to expand both its diagnostic possibilities and its utility in the interpretation of physiopathologic mechanisms. Conventional echocardiography is the more specific technique for the diagnosis of myocardial hypertrophy which, in turn, is one of the most important cardiovascular risk factors. The improvement of ultrasound technology may expand the possibility of noninvasive characterization of left ventricular hypertrophy by adding to the already known information about left ventricular mass and function, and that relative to the degree of hypertrophy-related fibrosis. In the present paper the authors reviewed the knowledge about biological and hemodynamic factors which contribute to the development and regression of myocardial hypertrophy. The possible role of new ultrasonic technology in the tissue characterization of myocardial hypertrophy is also discussed.