Left-ventricular peak ejection rate, filling rate, and ejection fraction--frame rate requirements at rest and exercise: concise communication

The effect of framing rate on the measurement of left-ventricular (LV) ejection fraction (EF), peak ejection rate (PER), and peak filling rate (PFR) was evaluated at rest and during exercise in 11 normal subjects and 21 patients who underwent gated equilibrium blood-pool imaging. Left-ventricular time-activity curves were obtained in each subject, at rest and during stress, at temporal resolutions of 10, 20, 30, 40, and 50 msec per frame. Ejection fraction, PER, and PFR were determined for each frame duration. By observing changes in the measured values of these quantities with framing rate we conclude that: a) for the measurement of EF, 50 msec per frame at rest and 40 msec per frame at exercise is sufficient; b) PER requires 40 msec per frame at rest and 20 msec per frame during exercise; and c) for the measurement of PFR, at least 40 msec per frame at rest and 20 msec per frame during exercise are needed. These results should hold for both first-pass and gated equilibrium studies.

Radionuclide cineangiography during stress

A "real-time" ECG-gated scintigraphic image system was developed at NIH, Bethesda. This system presents in real-time manner 1) an image sequence, that spans a complete heart cycle, 2) a regional time activity curve, in which later distolic phenomena are correctly portrayed, and 3) a beat length distribution function. This system is suitable especially for stress investigations. Normal subjects showed an increase of ejection fraction, whereas patients with CAD revealed a decrease of EF.

Exercise-induced left ventricular dysfunction in symptomatic and asymptomatic patients with aortic regurgitation: assessment with radionuclide cineangiography

In patients with aortic regurgitation,, left ventricular dysfunction at rest, which is associated with a poor long-term prognosis, often develops before severe symptoms. To determine whether evidence of left ventricular dysfunction could be detected before it appeared at rest, 43 patients with severe aortic regurgitation were studied using radionuclide cineangiography during exercise. In 30 normal subjects, left ventricular ejection fraction increased during exercise (57 +/- 1 percent [mean +/- standard error] at rest, 71 +/- 2 percent during exercise, P less than 0.001). In contrast, among 21 symptomatic patients, ejection fraction was normal at rest in 14 patients (average 47 +/- 2 percent) but normal during exercise in only one patient (average 38 +/- 2 percent, P less than 0.001). Ejection fraction was normal at rest in 21 of 22 asymptomatic patients (average 62 +/- 2 percent) but was normal during exercise in only 13 (average 57 +/- 3 percent, P less than 0.001). Thus, exericse-induced left ventricular dysfunction can precede symptoms and dysfunction at rest. Radionuclide assessment of left ventricular function during exercise may prove valuable in sequentially following the state of left ventricular function in patients before the onset of symptoms or of irreversible left ventricular failure.

Effects of self-induced starvation on cardiac size and function in anorexia nervosa

Cardiac size, function and rhythm were examined in 11 patients with anorexia nervosa. Mean left ventricular, left atrial and aortic dimensions on echocardiogram were below normal adult values at baseline. In addition to decreased cardiac dimensions--ventricular ectopy, relative hypotension, bradycardia and blunted heart rate--response to exercise were noted. Left ventricular systolic function, however, was unimpaired as indicated by normal echocardiographic fractional shortening, and by normal exercise augmentation of ejection fraction determined by radionuclide cineangiography. Eight of the patients responded to treatment with a mean weight gain of 32%. In these eight, cardiac dimensions increased toward normal: left ventricular dimension increased by 13%; left atrial dimension by 20%; aortic dimension by 15% and estimated left ventricular mass by 20%. We conclude that abnormalities of heart size and rhythm occur in patients with anorexia nervosa. However, cardiac dimensions, including left ventricular mass, may increase following nutritional rehabilitation, accompanied by an increase in heart rate and blood pressure.

Long-term hemodynamic and electrocardiographic assessment following operative repair of tetralogy of Fallot

To evaluate the long-term results of operative repair of tetralogy of Fallot, the cardiovascular, clinical, and electrocardiographic status was evaluated in 21 patients who had undergone operation 5 to 19 years previously. All patients were asymptomatic. Major functional abnormalities detected were enlarged right ventricular dimension in 15 of 17 patients, and elevated right ventricular systolic pressure during maximal exercise (mean, 69 +/- 5 mm Hg). Nevertheless, all patients had normal or nearly normal cardiovascular responses to maximal exercise as measured by cardiac output, maximal oxygen consumption, and left ventricular ejection fraction. Significant ventricular arrhythmias were detected during 24-hour ambulatory monitoring in 14 of 21 patients. Multiform ventricular premature beats (VPBs) were seen in 13 of 14 patients, couplets in four patients, greater than 30 VPBs for at least 1 hour in three, 4-complex ventricular tachycardia in one, and repeated R on T episodes in one. Although clinical and hemodynamic function was excellent in most patients, close follow-up is still necessary to determine the significance of the high-grade ventricular arrhythmias detected and if late manifestations of cardiovascular deterioration will occur.

Ejection fraction by count rate from gated images

Left-ventricular (LV) ejection fraction (EF) was determined from ECG-gated images of the cardiac blood pool, by computing the relative change in net LV counts occurring in these images during systole. EFs obtained with this method gave satisfactory interobserver agreement in 20 studies reviewed by three independent observers (average r = 0.95) and also compared favorably with EFs obtained by contrast ventriculography in 39 patients (r = 0.92). The technique appears suitable for use in the evaluation of systolic function in patients with heart disease.

Effects of coronary-artery bypass on global and regional left ventricular function during exercise

To determine the effect of coronary revascularization on exercise-induced abnormalities of left ventricular-ejection fraction and regional contraction, we obtained electrocardiograph-gated 99mTc radionuclide cineangiograms before and after operation in 23 consecutive patients. At rest, their average ejection fraction remained unchanged: 51 +/- 3 versus 54 +/- 4 per cent (+/- S.E.M.). However, 17 of the patients showed improvement of ejection fraction during postoperative exercise (increase of 51 per cent). The remaining six patients had no change or a decreased ejection fraction during exercise. All patients with improved ejection fractions during exercise were symptomatically improved. No improvement of regional function occurred at rest, but improvement did occur in regions of exercise-induced dysfunction. Although coronary revascularization has little effect on left ventricular function at rest, the ejection fraction during exercise and exercise-induced wall-motion abnormalities improve in most patients who experience symptomatic improvement.

Long-term anatomic fate of coronary-artery bypass grafts and functional status of patients five years after operation

To assess long-term results, coronary and graft angiography was performed 53 to 84 months after operation in 22 of 30 consecutive patients who had undergone coronary-artery bypass grafting before 1973, and who had at least one graft patent at an early (three to nine months) postoperative study. Of the 33 grafts, 31 were patent at late study. All patients had severe symptoms before operation. Of 16 who became asymptomatic early after operation, angina pectoris later redeveloped in 11. Progression of disease in ungrafted vessels accounted for symptomatic deterioration in nine of these 11 patients. We conclude that most grafts patent several months after operation remain so for at least 4 1/2 years, and that although most patients improve symptomatically after operation, symptomatic deterioration is common in the succeeding years and is most often due to progression of disease in ungrafted vessels.

Effect of nitroglycerin on exercise-induced abnormalities of left ventricular regional function and ejection fraction in coronary artery disease. Assessment by radionuclide clineagiography in symptomatic and asymptomatic patients

The effects of nitroglycerin (TNG) on exercise-induced abnormalities of left ventricular wall motion and ejection fraction are unknown in symptomatic and asymptomatic patients with coronary artery disease (CAD). In the present investigation radionuclide cineangiographic studies were performed in 47 patients with CAD (14 without angina during exercise) and in 25 normal subjects. All CAD patients, including those without symptoms, demonstrated regional wall motion abnormalities during exercise. In all patients, ejection fraction (EF) also responded abnormally to exercise: EF decreased from 48% at rest to 36% during exercise (P less than 0.001). EF increased in all normal subjects from an average of 58% at rest to 71% during exercise (P less than 0.001). In all CAD patients TNG reduced exercise-induced regional wall abnormalities and increased EF attained during exercise from an average of 36 to 48% (P less than 0.001). EF in normal subjects was unchanged by TNG. Thus, exercise can cause abnormalities in left ventricular regional function and ejection fraction in patients with or without symptoms; these abnormalities can be mitigated by prophylactic TNG.

Nitroglycerin-induced improvement in exercise tolerance and hemodynamics in patients with chronic rheumatic heart valve disease

Nitroglycerin reduces elevated left ventricular filling and pulmonary arterial pressures in resting patients with rheumatic valve disease and reduces symptoms when given over long periods to patients with primary myocardial disease. To determine whether nitroglycerin may prove effective therapeutically in ambulatory patients with heart valve disease, its effects on hemodynamics and exercise capacity were studied in 11 severely symptomatic adults who were already receiving optimal treatment with digitalis and diuretic agents. Seven had predominant mitral valve disease, one had predominant aortic insufficiency and three had equally severe mitral and aortic valve disease. Maximal exercise capacity was assessed with graded treadmill exercise after placebo and after nitroglycerin (0.5 mg sublingually) administered in random sequence to each patient. Exercise capacity (exercise time to limiting fatigue or dyspnea) increased from a mean of 8.3 minutes after placebo to 9.8 minutes after nitroglycerin (P less than 0.005). Eight patients were studied hemodynamically during further intense treadmill exercise. Pulmonary arterial pressure was significantly lower (P less than 0.05) after nitroglycerin than after placebo (mean 44 versus 56 mm Hg), but cardiac output was greater after nitroglycerin (5.0 versus 4.6 liters/min, P less than 0.005). Thus, nitroglycerin appears to increase exericse tolerance and improve the hemodynamic response to exercise in patients with heart valve disease and may be valuable in the long-term pharmacologic therapy of such patients.

Abnormal right ventricular size and ventricular septal motion after atrial septal defect closure: etiology and functional significance

Postoperative echocardiogram often demonstrate persistent right ventricular dilatation and paradoxic ventricular septal motion after repair of an atrial septal defect. To determine the prevalence, causes and significance of these echocardiographic abnormalities, 31 patients were studied with catheterization and echocardiography before and after repair of an atrial septal defect. Before operation, every patient manifested right ventricular dilatation, and all but one had abnormal septal motion. After operation, right ventricular dilatation was noted in 24 (77%) and abnormal septal motion in 21 (68%) patients despite the absence of residual left to right shunting in 30 (97%). These echocardiographic abnormalities could be correlated with age at operation and length of postoperative follow-up study but did not correlate with the degree of preoperative right ventricular enlargement or with shunt size or right ventricular pressure before or after operation. There was no associated functional deficit as demonstrated by the normal maximal oxygen consumption in all 13 patients who underwent treadmill exercise testing 5 to 38 months after operation; these patients included 9 with persistent right ventricular enlargement and abnormal septal motion.

ECG-gated scintillation probe measurement of left ventricular function

A nonimaging, ECG-gated scintillation-probe system is described that permits real-time quantification, at high temporal resolution, of the time variation of left ventricular (LV) volume over a complete, average cardiac cycle. Linearity between counting rate and volume, probe positioning, and background correction were investigated for both cylindrically collimated (CC) and parallel-hole-collimated (PC) detectors. In 53 patient studies, results obtained with these probes were compared with results obtained from an ECG-gated gamma camera system (CS) with high temporal resolution. Time-activity curves obtained by all three devices were essentially identical in shape (for CC against CS, r=0.93; for PC against CS, r=0.98) and in intracycle timing. Left-ventricular ejection fractions obtained with the probes showed workable agreement with the camera; for CC against CS, r=0.85 (N=31; for PC against CS, r=0.90 (N=21). When LV background is removed as a source of error, the correlation between (PC) probe and camera is improved (r=0.95, N=21). This suggests that the portable probe system be used in circumstances where exact knowledge of LV background is minimally important--e.g., continuous bedside monitoring of changes in LV function.

Real-time radionuclide cineangiography in the noninvasive evaluation of global and regional left ventricular function at rest and during exercise in patients with coronary-artery disease

Although coronary angiography defines regions of potential ischemia in patients with coronary-artery disease, accurate assessment of the presence and functional importance of ischemia requires appraisal of regional and global left ventricular function during stress. To perform such assessment, we developed a noninvasive real-time radionuclide cineangiographic procedure permitting continuous monitoring and analysis of left ventricular function during exercise. In 11 patients with coronary disease who had normal regional and global ventricular function at rest, new regions of dysfunction developed during exercise (P less than 0.001), and in 10, global ejection fraction dropped 7 to 47 per cent. Fourteen age-matched normal subjects were studied; during exercise none had regional dysfunction, and each increased global ejection fraction (average increase, 23 +/- 3 per cent [+/-S.E.], P less than 0.001 as compared with patients with coronary disease). Radionuclide cineangiography during exercise permits accurate assessment of the presence and functional severity of ischemic heart disease.

Echocardiographic observations in patients with systemic infiltrative disease involving the heart

Echocardiography was used to evaluate the heart in 19 patients with one of various systemic diseases known to be associated with infiltrative cardiomyopathy. Four patients had systemic amyloidosis, 10 had idiopathic hypereosinophilia and 5 had iron overload caused by multiple blood transfusions. Although 10 patients (53 percent) had no clinical evidence of cardiac disease, all 19 had echocardiographic abnormalities; the left ventricle was symmetrically thickened (more than 11 mm) and left ventricular mass was increased (more than 275 g) in all; the left ventricular transverse dimension was modestly increased (more than 52 mm) in 5 patients (26 percent) and the velocity of mitral valve closure in early diastole was reduced (less that 60 mm/sec) in 5 patients. Systolic function, as evidenced by ejection fraction, was well maintained (greater than 60 percent) in 18 of 19 patients. Thus, it appears that echocardiographic abnormalities can be detected in many patients with a systemic disease associated with infiltrative cardiomyopathy even before clinically evident heart disease develops.

A real-time system for multi-image gated cardiac studies

A minicomputer-based system is described that allows real-time construction and simultaneous display, in flicker-free movie format, of a cardiac-cycle-spanning sequence of ECG-gated scintigraphic images. In as little as 2 min, the endless-loop flicker-free movier clearly displays cardiac anatomy, time-dependent volume variations of cardiac chambers, and abnormalities of cardiac wall motion that would be difficult or impossible to detect from static gated images. Simultaneously, a time-activity curve with high temporal resolution can be generated from a previously defined region of interest, thereby quantifying additional parameters of cardiac function. Because the movie and time-activity curve are displayed in real time and require only a short data-collection interval to achieve statistical reliability, the physician can use the system interactively, modifying the form, intensity, or duration of diagnostic and therapeutic interventions based on the observed response. This system is well suited for intervention studies, for continuous cardiac monitoring, and for the rapid screening of patients with suspected cardiac disease.

Beneficial effect of lidocaine on ventricular electrical stability and spontaneous ventricular fibrillation during experimental myocardial infarction

Several studies have questioned the efficacy of lidocaine in reducing the incidence of ventricular fibrillation shortly after acute myocardial infarction when arrhythmogenic mechanisms may be different from those operative several hours later. To determine whether lidocaine inhibits the occurrence of early ventricular fibrillation, the left anterior descending and septal coronary arteries were occluded at their origins in open chest anesthetized dogs. Fourteen of 16 control dogs died with ventricular fibrillation. Fifteen dogs received two different dose regimens of lidocaine before coronary occlusion. Of the 11 treated dogs maintaining lidocaine bl), 6 survived (P less than 0.05). Five dogs received the larger dose; all died, four having blood levels of 6.3 mug/ml or greater at the time of death. Ventricular fibrillation threshold also increased in six of eight dogs when lidocaine was administered after coronary occlusion. It is concluded that lidocaine at blood levels of 1.2 to 5.5 mug/ml significantly reduces the incidence of ventricular fibrillation early after coronary occlusion. Administration of this agent therefore may be of particular value in the early phase of acute myocardial infarction.

Protection of ischemic myocardium by nitroglycerin: experimental and clinical results

Nitroglycerin (NTG) traditionally has bben avoided in the treatment of pain caused by acute myocardial infarction because of the belief that NTG-induced decrease in arterial pressure and concomitant reflex increase in heart rate might extend the ischemic process. However, recent experimental and clinical investigations cast doubt on this concept. For example, when the left anterior descending coronary artery is acutely occluded in normal dogs or in dogs when chronic coronary occlusions and extensive collaterals, NTG reduces ST-segment evevation (and presumably myocardial ischemia). This salutary effect occurs despite lowering of systemic arterial pressure, as long as excessive reflex tachycardia does not result; the magnitude of ischemia reduction is potentiated when methoxamine or phenylephrine are administered simultaneously to abolish the NTG -induced hypotension and reflex tachycardia. NTG and methoxamine treatment also results in 1) reduction of infarct size as (as assessed by gross morphologic examinations and myocardial CPK levels) in dogs subjected to 5 hours of coronary occlusion, and 2) increase in ventricular fibrillation (VF) threshold and reduction of the incidence of spontaneously occurring VF in dogs with acute coronary occlusion. Finally, the effectiveness of NTG during acute myocardial iinfarction (AMI) in man has been studied. Multiple precordial electrodes were used to measure changes in the degree of ST-segment elevation; these changes were used as an index of alterations in myocardial ischemic injury. Patients with normal pulmonary capillary wedge pressures ( less than 15 mm Hg) did not benefit consistently from NTG alone; however, when phenylephrine was administered with NTG (to abolish NTG-induced arterial pressure reduction and reflex increase in heart rate), ST-segment elevation diminished consistently. In patients with elevated wedge pressures ( greater than 15 mm Hg), NTG alone consistently reduced ischemia; addition of phenylephrine often partially reversed this benefit. Thus, administration of NTG, alone or with phenylephrine, appears to reduce myocardial ischemic injury during AMI in man; however, the response to phenylephrine depends upon the presence or absence of LV failure prior to treatment. These experimental and clinical results suggest this form of therapy may be use in reducing infarct size in man, although additional studies are necessary to determine the functional significance of these acute electrophysiologic alterations.