Cardiovascular response to acute airway obstruction and hypoxia.

We wished to evaluate the role of hypoxia in the production of cardiovascular manifestations of acute airway obstruction. We monitored blood pressure, electrocardiogram, and radionuclide ejection fraction in 14 healthy volunteers on exposure to four experimental conditions: expiratory resistive loading while breathing room air (RAL), expiratory resistive loading while hypoxic (HL), hypoxia alone (H), and expiratory resistive loading while voluntarily hyperventilating in a pattern similar to HL trials (VL). Mean respiratory-related oscillation in systolic blood pressure (pulsus paradoxus) increased significantly under each experimental condition compared with those at baseline (2 +/- 2.3 mm Hg): for RAL, 21 +/- 8.4 mm Hg; for HL, 34 +/- 16.3 mm Hg; for H, 10 +/- 5.4 mm Hg; for VL 26 +/- 13.4 mm Hg. Pulsus paradoxus was significantly greater under conditions of moderate hypoxia (saturation, 80%) than of mild hypoxia (saturation, 90%). Electrocardiographic changes were more marked under HL and H conditions than under RAL and VL conditions. HL induced changes in blood pressure and frontal QRS axis that were qualitatively similar to those seen in naturally occurring asthma. Radionuclide ejection fraction showed no dramatic change with any experimental condition. We conclude that hypoxia magnifies the cardiovascular changes induced by acute expiratory resistive loads and may contribute to the degree of pulsus paradoxus seen in severe asthma.

Effect of antianginal medications on the prognostic value of exercise thallium scintigraphy.

Whether administration of antianginal medications at the time of exercise thallium scintigraphy reduces the prognostic value of this test was retrospectively examined using two year follow-up of 201 patients. Sensitivity, specificity, positive and negative predictive values and accuracy of five test outcomes for prediction of coronary events (unstable angina, myocardial infarction, cardiac death) were compared between groups of patients either taking or not taking antianginal medications. Specificity and negative predictive value of exercise and redistribution thallium scores for prediction of coronary events were greater in patients not taking antianginal medication (P less than 0.05). It was concluded that normal exercise thallium scintigraphy affords greater assurance against future coronary events in patients tested while not taking antianginal medications.

Current management of congestive heart failure.

The author describes the pathophysiology of congestive heart failure and outlines treatment based on the mechanism and hemodynamics of heart failure. He discusses vasodilator therapy, ACE inhibitors in heart failure, and initiation of treatment. The paper concludes with a short discussion of methods of treating refractory heart failure.

Usefulness of radionuclide angiocardiography in predicting stenotic mitral orifice area.

Fifteen patients with pure mitral stenosis (MS) underwent high-temporal-resolution radionuclide angiocardiography for calculation of the ratio of peak left ventricular (LV) filling rate divided by mean LV filling rate (filling ratio). Whereas LV filling normally occurs in 3 phases, in MS it is more uniform. Thus, in 13 patients the filling ratio was below the normal range of 2.21 to 2.88 (p less than 0.001). In 11 patients in atrial fibrillation, filling ratio divided by mean cardiac cycle length and by LV ejection fraction provided good correlation (r = 0.85) with modified Gorlin formula derived mitral area and excellent correlation with echocardiographic mitral area (r = 0.95). Significant MS can be detected using radionuclide angiocardiography to calculate filling ratio. In the absence of the confounding influence of atrial systole calculation of 0.14 (filling ratio divided by cardiac cycle length divided by LV ejection fraction) + 0.40 cm2 enables accurate prediction of mitral area (+/- 4%). Our data support the contention that the modified Gorlin formula, based on steady-state hemodynamics, provides less certain estimates of mitral area for patients with MS and atrial fibrillation, in whom echocardiography and radionuclide angiocardiography may be more accurate.

Echocardiographic abnormalities following cardiac radiation.

Five years or more after receiving cardiac radiation, 41 patients with Hodgkin's disease and seminoma in remission were subjected to echocardiography. The abnormalities detected included pericardial thickening in 70%, thickening of the aortic and/or mitral valves in 28%, right ventricular dilatation or hypokinesis in 39%, and left ventricular dysfunction in 39%. In the 23 patients treated by an upper mantle technique with shielding, the incidence of right ventricular abnormalities and valvular thickening was significantly lower than in patients treated with modified techniques. Although no symptoms were attributable to the observed abnormalities, longer follow-up time may reveal important functional implications.

Optimized count-based scintigraphic left ventricular volume measurement.

Count-based scintigraphic left ventricular end-diastolic (LVED) volume measurement was optimized using a reproducible method for determining left ventricular counts and an independently measured average apparent tissue attenuation coefficient (0.16 cm-1). Tissue depth was calculated by triangulation. Results were compared to single-plane contrast ventriculographic volumes by an area-length method, performed within one hour, in 18 patients. The overall correlation of measurements of LVED volume by the 2 methods was 0.96 with standard error of the scintigraphic estimate of 15.8 ml. For 6 patients with angiographically normal wall motion, the correlation of volume measurements was 0.99 with standard error of the estimate of 5.1 ml. The mean absolute difference in LVED volume by the 2 methods was 3.8 ml in the group with normal wall motion compared to 19.2 ml in the 12 patients with angiographically abnormal wall motion. Area-length LVED volume calculation assumes that the left ventricle conforms to a standard shape. Discrepancies in volume estimates with abnormal ventricular wall motion suggest that the area-length method is less accurate. Optimized count-based LVED left ventricular volume measurement is accurate and might be preferable to single-plane contrast angiographic volume measurement of abnormal ventricles.

Mitral valve replacement for mitral regurgitation with and without preservation of chordae tendineae.

Left ventricular function was compared in 15 patients who had conventional mitral valve replacement (Group 1) and 12 patients who had replacement with preservation of chordae tendineae and papillary muscles (Group 2) for isolated chronic mitral regurgitation. Function was assessed by radionuclide ventriculography. The two groups were similar in terms of age, preoperative functional class, valve pathology, and preoperative left ventricular function. There was uniform intraoperative and postoperative management by a single surgeon. All patients received porcine bioprostheses. Left ventricular function was assessed 1 day before and 3 to 6 months after the operation. Left ventricular ejection fraction decreased from 0.55 +/- 0.09 to 0.48 +/- 0.14 in Group 1 (p less than 0.01) and did not change significantly in Group 2 (from 0.53 +/- 0.14 to 0.52 +/- 0.16). Left ventricular end-diastolic volume, end-systolic volume, and stroke volume indices decreased significantly in both groups. During maximal postoperative bicycle exercise with the patient supine, left ventricular ejection fraction and stroke volume index increased significantly in Group 2 only. Cardiac output increased in both groups during exercise, but this increase was due to increased heart rate in Group 1 and to increased heart rate and stroke volume in Group 2. These findings suggest that preservation of chordae tendineae and papillary muscles during mitral valve replacement for chronic mitral regurgitation has a beneficial effect on postoperative left ventricular function.

The value of nuclear angiography in the preoperative assessment of patients undergoing elective aortic surgery.

Eighteen patients undergoing elective aortic surgery, either for peripheral vascular insufficiency or abdominal aneurysm, were studied preoperatively by nuclear angiography. By this technique the resting ventricular function of each patient was measured. Nuclear angiography is a safe non-invasive technique which has been shown to have excellent correlation with conventional contrast angiography in the assessment of ejection fraction. Throughout the intraoperative period, measurements of the central venous pressure and pulmonary capillary wedge pressure were taken simultaneously at approximately five-minute intervals. An average of 18 data points was established in each case. The correlation between central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) was examined. Ten of our patients had preoperative resting ejection fractions less than 55 per cent. In only four of these patients (40 per cent) was correlation between CVP and PCWP judged to be good intraoperatively. Eight of our patients had preoperative ejection fractions greater than 55 per cent. Six of these (75 per cent) showed good correlation between CVP and PCWP intraoperatively. We also assessed our ability to predict by purely clinical means which patients would show poor correlation between CVP and PCWP. Evaluation on purely clinical grounds was as good as the scans at predicting in which patients CVP would not correlate with PCWP and we feel that the routine use of this test would not modify our use of Swan Ganz catheters for intraoperative monitoring in patients undergoing aortic surgery, in the future.

Analysis of adults with and without complex ventricular arrhythmias after repair of tetralogy of Fallot.

Forty-four adult patients with tetralogy of Fallot were studied while clinically well at a mean of 14 years (range 5 to 27) after intracardiac repair to examine the association of postoperative ventricular arrhythmias with historical and postoperative hemodynamic data. Twenty-two patients who demonstrated during 24 hour ambulatory monitoring or maximal graded treadmill exercise testing, or both, ventricular premature beats that were multiform, repetitive or increased in frequency during exercise or recovery after exercise were found to differ from patients without such ventricular premature beats in four respects. The patients with complex or exercise-induced ventricular premature beats had a higher right ventricular systolic blood pressure, a higher incidence of residual left to right intracardiac shunt, lower cardiac index and more frequently abnormal left ventricular ejection fraction measured by rest and exercise-gated radionuclide ventriculography. Adults with complex or exercise-induced ventricular premature beats after intracardiac repair of tetralogy of Fallot are characterized by suboptimal hemodynamic repair and preclinical left ventricular dysfunction.

Clinically unrecognized ventricular dysfunction in young diabetic patients.

Left ventricular function at rest and during supine bicycle exercise was assessed by gated radionuclide angiography in 20 diabetic patients and 18 normal control subjects without clinical evidence of heart disease. The diabetic patients were aged 21 to 44 years and all except one used insulin. No subject developed chest pain or electrocardiographic changes during exercise. Both groups had a similar rest and exercise heart rate and blood pressure, and both achieved similar work loads. The control group had an ejection fraction at rest of 65.4 +/- 6.2% (mean +/- SD) and only 1 of 18 showed a decrease with exercise; peak exercise ejection fraction averaged 77.1 +/- 7.8%. The diabetic group had a mean ejection fraction at rest of 63.7 +/- 6.5%, similar to that of the control group, but 7 of 20 showed a decrease during exercise; the exercise ejection fraction averaged 67.7 +/- 9.7%, significantly lower than that of the control group (p less than 0.01). The diabetic patients varied widely in ejection fraction response to exercise, ranging from an increase of 25% to a decrease of 21%. This response did not correlate with age, sex, duration of diabetes, smoking, retinopathy, exercise heart rate, blood pressure or rate-pressure product, work load attained or ejection fraction at rest. These data suggest that approximately one-third of patients with diabetes have subclinical left ventricular dysfunction without correlation to risk factors for atherosclerosis or other diabetic complications. Whether this is due to unrecognized coronary artery disease or primary myocardial disease remains unknown.

Radionuclide angiography and endomyocardial biopsy in the assessment of doxorubicin cardiotoxicity.

Thirty-eight patients with a mean age of 53.2 years (19 to 75 years of age), who were receiving doxorubicin (D) for malignant disease, were studied in order to determine the relationship between functional and morphologic myocardial changes at different dose levels. Serial patient evaluations included physical examination, chest x-ray, electrocardiogram (ECG), endomyocardial biopsy (EMB), and rest-exercise gated nuclear angiography (GNA), at doses of D ranging from 144 to 954 mg/m2 (mean, 426 mg/m2). Physical examination, chest x-ray, and ECG proved to be insensitive predictors of D cardiotoxicity. Correlation of GNA and EMB in 31 patient evaluations, exclusive of known heart disease, did not reveal any false-positive angiograms, and all abnormal GNAs were associated with abnormal biopsies. Use of stress GNA uncovered six abnormal ventricles which could have been missed with a rest GNA alone. It has been suggested that: (1) GNA is a reliable monitor of D therapy; (2) an exercise study should be performed when the rest ejection fraction is normal, but is unnecessary when the rest EF is abnormal; (3) all patients with a resting ejection fraction of less than 45%, exclusive of other cardiac disease, should have D discontinued; and (4) endomyocardial biopsy is useful in assessing D cardiotoxicity in patients with other possible causes of an abnormal GNA.

Repeatability of estimates of left-ventricular volume from blood-pool counts: concise communication.

Radionuclide ventriculography permits nongeometric calculation of ventricular volume. Accurate and reproducible determination of left-ventricular (LV) blood-pool counts is necessary to perform this calculation. Furthermore, to make serial volume determinations one must know the half-time of in vivo blood-pool activity. We compared five methods of LV count determination in nine patients. Interpatient and intrapatient variability of the in vivo half-time of Tc-99m-labeled red blood cells (RBCs) was measured. Left-ventricular count determinations, derived from temporally and spatially smoothed images using a second-derivative algorithm to identify the LV region of interest (ROI), are less variable than those based on manual ROI determinations. The mean in vivo half-time of Tc-99m RBCs is 4.1 hr, and there is significant interpatient (0.9 +/- 0.8 hr) and intrapatient (1.0 +/- 0.9 hr) variability. These findings should be considered in the determination of serial, relative ventricular volume by radionuclide ventriculography.

Detection of radiation cardiomyopathy by gated radionuclide angiography.

Twenty-one asymptomatic adults underwent rest and exercise gated radionuclide angiography seven to 20 years after having received mediastinal radiation (2,000 to 7,600 rads) for Hodgkin's disease. None of these patients received cytotoxic chemotherapy. Twelve patients (57 percent) had abnormal left (less than 53 percent at rest and/or greater than 5 percent decrease at peak exercise) and/or right (less than 27 percent at rest and/or greater than 5 percent decrease at peak exercise) ventricular ejection fractions. Previous reports have described myocardial fibrosis occurring late after therapeutic mediastinal radiation; however, the incidence of this occurrence based on clinical follow-up has been low. Rest and exercise radionuclide angiography is a sensitive method for assessing systolic ventricular function and reveals a high prevalence of cardiomyopathy that can be linked to previous radiotherapy.

Rest and exercise ventricular function in adults with congenital ventricular septal defects.

Rest and exercise right and left ventricular function were compared using equilibrium gated radionuclide angiography in 19 normal sedentary control subjects (mean age 28 years, range 22 to 34) and 34 patients with hemodynamically documented congenital ventricular septal defect (VSD) (mean age 27 years, range 20 to 40). The 34 patients with VSD were divided into 3 groups: those in Group 1 (17 patients) had pulmonary to systemic blood flow ratios of less than 2 to 1; those in Group 2 (12 patients) had prior surgical closure of VSD (mean interval from surgery 17 years, range 9 to 22), and those in Group 3 (5 patients) had Eisenmenger's complex. Gated radionuclide angiography was performed at rest and during each level of graded supine bicycle exercise to fatigue. Heart rate, blood pressure, maximal work load achieved, and right and left ventricular ejection fractions were assessed. The control subjects demonstrated an increase in both the left and right ventricular ejection fractions with exercise (0.70 +/- 0.07 to 0.79 +/- 0.05 and 0.46 +/- 0.06 to 0.57 +/- 0.04; p less than 0.001 for left and right ventricles, respectively). All study groups failed to demonstrate an increase in ejection fraction in either ventricle with exercise. Furthermore, resting left ventricular ejection fraction in Groups 2 and 3 was lower than that in the control subjects (0.59 +/- 0.09 and 0.54 +/- 0.06 versus 0.70 +/- 0.07; p less than 0.001) and resting right ventricular ejection fraction was lower in Group 3 versus control subjects (0.30 +/- 0.07 versus 0.46 +/- 0.06; p less than 0.001). Thus (1) left and right ventricular function on exercise were abnormal in patients with residual VSD as compared with control subjects; (2) rest and exercise left ventricular ejection fractions remained abnormal despite surgical closure of VSD in the remote past; (3) resting left and right ventricular function was abnormal in patients with Eisenmenger's complex; (4) lifelong volume overload may be detrimental to myocardial function.

Assessment of right ventricular function during supine bicycle exercise after Mustard's operation.

Right ventricular (RV) performance during supine bicycle exercise was evaluated by gated equilibrium nuclear angiography in 19 clinically well children with d-transposition of the great arteries (d-TGA), 6.4 +/- 2.7 years after Mustard's operation. Comparisons were made between rest and peak exercise. The mean resting ejection fraction was 44 +/- 12% (range 30-75%) and was unchanged at peak exercise. Eight children had a normal ejection fraction response, whereas 11 children had either no increase or a decrease in ejection fraction. Relative end-diastolic volumes decreased from resting values in all patients who had an abnormal ejection fraction response. Among patients whose ejection fraction increased, the end-diastolic volume increased in three, decreased in four and was unchanged in one at peak exercise. Heart rate increased 84% (range 52-135%) and systolic blood pressure increased 16% (range 0-28%) at peak exercise. There was no correlation between exercise response and age at surgery or interval since surgery. These data indicate that clinically well children after Mustard's procedure may have abnormal right ventricular function under stress, raising concerns about the ability of the right ventricle to function as the systemic ventricle.

Left ventricular function in trained and untrained healthy subjects.

Left ventricular function was compared in 18 normal sedentary controls (mean age 28 years, range 22 - 34 years) and nine endurance-trained athletes (mean age 19 years, range 15 - 25 years) at rest and during supine bicycle exercise. Gated radionuclide angiocardiograms were performed at rest and at each level of graded maximal supine bicycle exercise. Heart rate, blood pressure, left ventricular ejection fraction and the relative changes in left ventricular end-diastolic and end-systolic volumes were assessed. Athletes attained a much greater work load than controls (mean 22.1 kpm/kg body weight vs 13 kpm/Kg body weight). Both groups achieved similar increased in heart rate, blood pressure and ejection fractions. In the controls, the mean end-diastolic volume increased to 124% of that at rest (p less than 0.02) during exercise and the mean end-systolic volume decreased to 81% of the rest level (p less than 0.02). In contrast, the mean end-diastolic volume did not significantly change during exercise in the athletes, and the mean end-systolic volume decreased to 64% of rest (p less than 0.05). Thus, although trained and untrained healthy subjects had similar increases in the left ventricular ejection fraction during exercise, different mechanisms were used to achieve these increases. Untrained subjects increased end-diastolic volumes, whereas trained subjects decreased the end-systolic volumes. The ability of athletes to exercise without increasing preload may be an effect of training amd might have important implications in reducing myocardial oxygen demand during exercise.