Left ventricular function during exercise testing and training.

Left ventricular function (LVEF) deteriorates during incremental exercise (GXT) in patients with ischemia (+ISCH). Left ventricular (LV) functional response during steady-state exercise, typical of that used in exercise training, are unknown. We compared LVEF in patients with documented coronary heart disease (CHD) who either had (+) or did not have (-) ISCH, and in healthy volunteers (CONTROL) during GXT and steady state. First pass RNA was performed during upright cycle GXT at rest (R), at the ventilatory threshold (VT), and at maximal exercise (Max); and during steady state at the workload associated with VT after 10, 20, and 30 min of exercise. RNA allowed measurement of ejection fraction (EF) and wall motion (WM); ISCH was mild, angina being relieved by momentary reductions in workload during steady state. Although +ISCH demonstrated the expected deterioration in LV function during GXT (decreased EF, abnormal WM)(EF = 58 to 56 to 54%), there was no evidence for progressive deterioration of LV function during steady state despite the presence of mild ISCH (56 to 56 to 54 to 54%). In -ISCH and CONTROL there were normal responses of EF during GXT (43 to 51 to 51% and 59 to 65 to 61%) and steady state (43 to 51 to 53 to 51% and 59 to 65 to 68 to 69%). We conclude that mild ischemia may be tolerated during steady-state exercise at levels consistent with exercise training without progressive deterioration of LV function.

Left ventricular ejection fraction during incremental and steady state exercise.

Despite extensive study of left ventricular (LV) function during incremental exercise (INC), there is little known about LV function during steady state exercise typical of that used during exercise training. In this study we evaluated LV ejection fraction (LVEF) during upright cycle ergometer exercise using first-pass radionuclide angiography (RNA). Healthy volunteers (N = 10) were studied during both INC and steady state. INC studies were performed at rest, at the ventilatory threshold (VT), and at maximal exercise. During steady state studies were performed after 10, 20, and 30 min of exercise at VT. During INC LVEF increased from rest (61% +/- 5%) to exercise at the VT (73% +/- 5%). There was no further change in LVEF at maximal exercise (73% +/- 5%). During steady state, LVEF increased from rest (61% +/- 5%), to exercise at VT (73% +/- 5%), with further increases after 20 (78% +/- 6%) and 30 (79% +/- 3%) min of exercise. The results suggest that LVEF is nearly maximal during submaximal exercise at VT. During steady state LVEF continues to increase with continuation of steady state exercise.

Fee-for-service versus capitation-based reimbursement: how the payment method affects utilization of echocardiographic services by referring physicians.

Historically, health insurance carriers (HIC) have reimbursed physicians on a fee-for-service basis for echocardiographic studies. With the emergence of managed care, the HIC now may have the option of paying on a capitation basis. To determine whether the method of reimbursement had any bearing on the types of patients referred for echocardiographic services, we conducted a two-phase (retrospective) study. In Phase One, we assessed two groups of ambulatory patients with regard to patient characteristics, medical reason for referral, and echocardiographic results. Group A (4,066 patients) had insurance plans that stipulated reimbursement for echocardiographic services as part of capitation for cardiology services. Group B (3,061 patients) had plans that reimbursed for echocardiographic services on a fee-for-service basis. In Phase Two, we assessed a total of 5,947 patients (3,833 from Group A and 2,114 from Group B) over a period of 40 months to determine the frequency of referral for a second echocardiogram within 2 years of a normal one and the repeat normalcy rate. The results showed that the capitation reimbursement group included younger, predominantly female patients who were referred more often for a more benign reason and who more frequently were diagnosed echocardiographically with less severe disease, higher rates of normalcy, and repeat normalcy. These findings suggest that in our geographic area the capitation method of reimbursement permitted more liberal utilization of echocardiographic services. In this era of cost awareness, the study suggests the need for better screening of patients referred for echocardiographic services.

Left ventricular volume calculation using a count-based ratio method applied to first-pass radionuclide angiography.

Most count-based radionuclide methods for calculating left ventricular volume rely on measurement of radioactivity in a peripheral blood sample and a measurement of ventricle to collimator distance. We have developed a method which requires neither a blood sample nor a distance measurement and which is applicable to first-pass radionuclide angiography. The parameters used to calculate volume are the area of pixel, the total counts in the left ventricle and the maximum pixel count. The equation was used to calculate the volumes in 50 patients who had both resting first-pass radionuclide angiography (25 patients with a single crystal and 25 patients with a multicrystal camera) and contrast ventriculography on the same day. Correlation coefficients for end-diastolic and end-systolic volumes showed r ranging 0.93-0.98 and standard error of estimate ranging 23-35 ml for end-diastolic volume (14%-17% of mean end-diastolic volume) and 16-23 ml for end-systolic volume (18%-21% of mean end-systolic volume). Image processing software for extracting the needed values is generally available on most commercial nuclear medicine imaging systems and the additional time for the calculations is short. Although the theory is based on multiple assumptions, the volume calculation appears to be reasonably accurate and clinically applicable.

Long-term prognostic value of a normal dipyridamole thallium-201 perfusion scan.

In a 4-year period, 84 patients who were referred for a dipyridamole thallium-201 stress test to rule out significant coronary artery disease had normal scans. A dipyridamole study was recommended instead of exercise because of arthritis, severe obesity, peripheral vascular disease, pulmonary disease, other chronic illnesses, or combinations of these problems. All patients had three-view (i.e., anterior, shallow left anterior oblique, and steep left anterior oblique) planar thallium-201 imaging 10 minutes and 3.5 hours after administration of 0.6 mg/kg of intravenous dipyridamole. The patients were followed for 42 +/- 13 (range 1-58) months to document the cardiac event rate. Of the 84 patients with normal results, 14 died during the follow-up period from noncardiac causes. Three other patients died 29-51 months after the test due to an acute myocardial infarction, a probable acute myocardial infarction, and sudden cardiac death, respectively. Of the survivors, 5 suffered an acute myocardial infarction 28-50 months after the dipyridamole thallium scan and 1 had coronary artery bypass grafting due to increasing angina pectoris 58 months after the scan (overall cardiac event rate of 0.4% per year). Of the remaining 61 patients, 39 (64%) were asymptomatic, 20 (33%) had the same symptoms they had at the time of testing without significant deterioration, while 2 patients (3%) had deterioration of their chest pains but no cardiac complication. Thus, in this group of patients, a normal dipyridamole thallium-201 perfusion scan predicted a good cardiovascular outcome for at least 24 months following the test.

Coronary vasodilator reserve. Comparison of the effects of papaverine and adenosine on coronary flow, ventricular function, and myocardial metabolism.

To evaluate coronary flow reserve during cardiac catheterization, intracoronary adenosine and papaverine have been used in the clinical setting. Although papaverine maximizes coronary blood flow, it induces several toxic side effects that reduce its desirability as a coronary dilator. This investigation was designed to compare the subselective intracoronary administration of papaverine with that of adenosine in an animal model. In dogs (n = 34), we studied the effects of each agent on hemodynamics, regional myocardial blood flow, contractility (sonomicrometric and echocardiographic), metabolism (coronary arterial and venous lactate and tissue high-energy phosphates), and electrocardiographic (ST and QT intervals) parameters. Barbiturate and morphine anesthesia/analgesia was induced, and a left thoracotomy was performed. An arterial shunt was created from the left carotid artery to the left anterior descending coronary artery. Two separate groups were studied: group 1 (n = 16) for regional myocardial blood flow and mechanical function and group 2 (n = 18) for biochemical measurements. Adenosine (67 +/- 2 micrograms/min) or papaverine (6 +/- 1 mg/min) was infused into the coronary shunt at a rate of 0.5 + 0.1 ml/min for a maximum duration of 3.5 minutes. Regional myocardial blood flows were determined at control (predrug) and maximal coronary flow using radiolabeled microspheres. All hemodynamic, wall motion, biochemical, and electrocardiographic parameters were also measured at these times. Both drugs produced comparable increases in total and regional coronary blood flows (adenosine, 1.21 +/- 0.15 to 4.83 +/- 0.36 ml/min/g; papaverine, 1.21 +/- 0.05 to 4.89 +/- 0.28 ml/min/g) upon infusion into the left anterior descending coronary artery. Papaverine produced significant (p less than 0.05) changes in subendocardial ST segment electrocardiogram (-2.5 mm), QT prolongation (8 +/- 2%), myocardial creatine phosphate (47% decrease), and coronary sinus serum lactate (277% increase) compared with control. In addition, intracoronary papaverine induced an abnormal contractile pattern. No significant changes in any of these parameters (i.e., ST segment, QT prolongation, myocardial creatine phosphate level, or lactate level) were observed with intracoronary adenosine infusions. We conclude that intracoronary adenosine is comparable to papaverine for maximizing coronary blood flow without the deleterious properties observed with intracoronary papaverine.

Mitral regurgitation: parameters that affect the correlation between Doppler echocardiography and contrast ventriculography.

The correlation between Doppler and contrast angiographic estimation of severity of mitral regurgitation was assessed retrospectively in 60 patients with native mitral valve disease. Results showed r = 0.82. Among 15 parameters (demographic, clinical, echocardiographic and hemodynamic) 3 were found to be associated with overestimation of the severity by Doppler: low left ventricular ejection fraction, low cardiac output, and high mean pulmonary artery capillary wedge pressure. On the other hand, a large left atrium was associated with underestimation of mitral regurgitation by Doppler. Based on that data, Doppler results were adjusted in a prospective group of 30 patients with native mitral valve disease. The correlation between contrast ventriculography and uncorrected Doppler results showed r = 0.83, while the corrected Doppler results showed r = 0.91. The study implies that although a good correlation is found between the two modalities for estimation of mitral regurgitation, a better correlation can be achieved by adjusting the Doppler results according to the above-mentioned parameters.

Left ventricular volume calculation using a count-based ratio method applied to multigated radionuclide angiography.

The purpose of this study was to investigate the accuracy of a new count-proportional method for the measurement of left ventricular volume when applied to gated equilibrium blood-pool imaging. An equation is developed that relates total chamber volume, Vt, to the area of a pixel (M) and the ratio (R) of total counts within the chamber to the counts within the hottest pixel in the chamber such that Vt = 1.38 M3R3/2. The value of M is a constant for the particular scintillation camera-collimator system and R is obtained from observed count rates. All calculated volumes were compared to volumes measured using biplane contrast ventriculography. In 25 patients, the method for ventricular volumes gave an r of 0.95 and an s.e.e. of 23 ml [Volume (nuclear) = 0.94 Volume (cath) + 1.3]. Endsystolic volume was best calculated from end-diastolic volume and ejection fraction. Manual regions of interest were more accurate than automated regions of interest. This method appears to be as accurate as more complex approaches and has the advantage of not requiring attenuation correction or blood sampling.