Prolonged decrease in cardiac volumes after maximal upright bicycle exercise

Sequential exercise-gated cardiac blood pool scintigrams provide a noninvasive technique for evaluating the effect of therapeutic interventions on cardiac volumes and function only if both exercise periods are equivalent in the absence of an intervention. To assess whether they are indeed equivalent, 14 healthy subjects underwent gated blood pool scintigraphy during two maximal upright exercise periods separated by 60 min without changing position. Although resting cardiac output and blood pressure returned to base-line values 60 min after the first exercise period, mean resting heart rate was markedly higher (89.4 +/- 2.7 vs. 66.5 +/- 2.5 beats/min, P less than 0.001) and upright cardiac volumes lower [39.1 +/- 4.9 vs. 56.3 +/- 6.0 ml, P less than 0.001, for end-systolic volume (ESV) and 112.6 +/- 8.0 vs. 144.9 +/- 9.0 ml, P less than 0.001, for end-diastolic volume (EDV)] than before the first exercise period. These differences persisted during low levels of the subsequent exercise but not at high and maximum work loads. Cardiac volumes and heart rate 60 min after an identical exercise protocol in a second group of 22 subjects who received propranolol, 0.15 mg/kg iv, after their initial exercise, however, were the same as those preexercise. Thus higher sympathetic tone may be responsible for the persistently higher heart rate and decreased cardiac volumes after exercise, and the assumption that cardiac volumes and function are similar during two closely spaced sequential exercise studies is not always valid.

Exercise-induced arrhythmias in diuretic-treated patients with uncomplicated systemic hypertension

Although hypertensive patients have been shown to have a higher prevalence of arrhythmias during ambulatory monitoring when treated with diuretic drugs than when untreated, the effects of maximal aerobic stress on arrhythmia frequency in such patients is unknown. The incidence of arrhythmias during graded maximal treadmill exercise in a group of 68 subjects with mild, clinically uncomplicated systemic hypertension treated chronically with diuretics alone for a median of 4.5 years was compared with that in an age-matched normotensive control group. The prevalence of exercise-induced arrhythmias was higher in the group treated with diuretics than in the control group, 57% vs 38% (p less than 0.05). This difference was entirely due to the higher incidence of isolated atrial or ventricular premature complexes in the diuretic-treated patients, 44% vs 26% (p less than 0.05). There was no difference in the incidence of frequent (more than 10% of beats) or complex supraventricular or ventricular premature complexes between the diuretic-treated and control groups. Within the diuretic group, no difference in the incidence of simple or complex arrhythmia was found between men and women, between those with and those without rest or exercise-induced electrocardiographic abnormalities or between those with a serum potassium level of less than 3.7 mEq/liter vs those with a level of 3.7 mEq/liter or greater. Thus, patients with uncomplicated hypertension treated with chronic diuretic monotherapy do not appear to be at increased risk for major arrhythmias during aerobic exercise.

Use of the Frank-Starling mechanism during submaximal versus maximal upright exercise

To evaluate the extent to which the Frank-Starling mechanism is utilized during successive stages of vigorous upright exercise, absolute left ventricular end-diastolic volume and ejection fraction were determined by gated blood pool scintigraphy at rest and during multilevel maximal upright bicycle exercise in 30 normal males aged 26-50 yr, who were able to exercise to 125 W or greater. Left ventricular end-systolic volume, stroke volume, and cardiac output were calculated at rest and during each successive 3-min stage of exercise [25, 50, 75, 100, and 125-225 W (peak)]. During early exercise (25 W), end-diastolic and stroke volumes increased (+17 +/- 1 and +31 +/- 4%, respectively), with no change in end-systolic volume. With further exercise (50-75 W) end-diastolic volume remained unchanged as end-systolic volume decreased (-12 +/- 4 and -24 + 5%, respectively). At peak exercise end-diastolic volume decreased to resting level, stroke volume remained at a plateau, and end-systolic volume further decreased (-48 +/- 7%). Thus the Frank-Starling mechanism is used early in exercise, perhaps because of a delay in sympathetic mobilization, and does not appear to play a role in the later stages of vigorous exercise.

Unexplained sinus bradycardia: clinical significance and long-term prognosis in apparently healthy persons older than 40 years

The significance of sinus bradycardia (SB) in clinically healthy, non-endurance-trained, middle-aged and older persons is unknown. From 1,172 normal volunteers, aged 40 to 96 years, enrolled in the Baltimore Longitudinal Study of Aging, 47 subjects, aged 58 +/- 13 years, with SB (less than 50 beats/min) were identified by rest electrocardiography and were compared with a group of control subjects matched for age and sex. The prevalence of unexplained SB was approximately 4% and was nearly identical in men and women. At the latest follow-up examination, after a mean follow-up of 5.4 years, the SB group had a higher prevalence of associated conduction abnormalities (first-degree atrioventricular [AV] block, left-axis deviation, and complete or incomplete right bundle branch block) than the control group (43% vs 19%, p less than 0.05). On maximal treadmill exercise testing, performed in 44 patients within 1 visit of their most recent examination showing SB, maximal heart rate (157 +/- 18 beats/min) did not differ significantly from that of control subjects (163 +/- 19 beats/min); exercise duration, however, was greater in the former group, 11.0 +/- 2.8 vs 9.7 +/- 3.1 minutes (p less than 0.05). No patients with SB had syncope, high-degree AV block or other manifestation of sick sinus syndrome during follow-up. Angina pectoris, myocardial infarction, congestive heart failure or cardiac death occurred in 8% of patients with SB and 11% of control subjects over the observation period (difference not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

CHF: reflections on current management of the older patient

The deleterious effects of prolonged bedrest on aerobic capacity, mineral balance, and various metabolic processes have been amply demonstrated. Since these functions are already compromised by aging per se, complete or prolonged bedrest should be avoided in geriatric cardiac patients if at all possible, regardless of their specific diagnosis. Diuretics are still the mainstay therapy for CHF. For elderly patients with mild CHF and preserved renal function, a thiazide rather than a loop diuretic appears preferable, due to more gentle diuresis and lower frequency of side effects.

Prevalence and significance of postexercise hypotension in apparently healthy subjects

Although a decrease in systolic blood pressure (BP) occurring during treadmill exercise is often a sign of severe left ventricular dysfunction, the prevalence and significance of postexertional hypotension is unclear. The postexercise systolic BP response to maximal treadmill exercise was analyzed in 781 asymptomatic volunteers, aged 21 to 96 years (mean 51 +/- 16) from the Baltimore Longitudinal Study on Aging. Fifteen subjects (1.9%) had a postexercise decrease in systolic BP of at least 20 mm Hg from preexercise sitting values, to a level of 90 mm Hg or less. The prevalence of postexercise hypotension was 3.1% (14 of 449) in subjects younger than 55 years, but only 0.3% (1 of 332) in those older than 55 (p less than 0.01). Before exercise these 15 subjects demonstrated a slight orthostatic decrease in systolic BP of -1.7 +/- 4.8 mm Hg compared with an increase of 5.3 +/- 5.1 mm Hg in age-matched control subjects (p less than 0.001). The lowest systolic BP averaged 78 +/- 9 mm Hg (range 62 to 90) and occurred between 4 and 9 minutes after exercise in 80% of cases. All but 3 episodes were symptomatic, with dizziness dominant. In only 2 subjects was the hypotension associated with vagal symptoms and bradycardia. Compared with control subjects, subjects with postexercise hypotension had higher maximal heart rates (184 +/- 15 vs 173 +/- 11 beats/min, p less than 0.05), but showed no difference in exercise tolerance or systolic BP at submaximal or maximal effort. Postexercise ST-segment abnormalities suggesting ischemia occurred in one-third of the hypotensive subjects but none of the control subjects (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in cardiovascular structure and function with advancing age

The greatest difficulty in studying the effects of aging on cardiovascular structure and function lies in separating the effects of aging itself from those of the inextricably entwined disease processes and life-style changes that accompany aging. Age-related stiffening of the arterial tree results in an increased systolic blood pressure, which appears to impose a greater load on the heart. Probably as an adaptive mechanism to maintain normal wall stress, a modest age-associated concentric left ventricular hypertrophy develops, which approximates 30% between ages 25 and 80. The decrease in mitral valve E-F slope and increase in the left atrial dimension, which are seen with advancing age, may be construed as the consequences of a thicker-walled, less compliant left ventricle. Systolic left ventricular function, measured at rest either by echocardiography or radionuclide techniques, is unaffected by aging. Aerobic exercise capacity, whether measured as total work performance or maximal oxygen consumption declines with age, although in subjects who maintain a high level of physical activity, the decline appears to be approximately half of the 10% per decade decrease seen in sedentary persons. An age-related decline in maximal exercise heart rate has been a universal finding. Although several studies over the past 4 decades have found cardiac output to decrease with age, both at rest and during exercise, a recent study of subjects carefully screened to exclude latent coronary artery disease found no such decline in cardiac output. In these subjects, the age-related decline in maximal heart rate and systolic emptying at peak exercise was offset by an increased utilization of the Frank-Starling mechanism. An attractive hypothesis for explaining the hemodynamic profile of a decreased maximum heart rate, increased preload and decrease in ejection fraction at maximal effort, despite elevated norepinephrine levels, is an age-associated, diminished end-organ responsiveness similar to beta-adrenergic blockade.

Postural changes in cardiac volumes in men in relation to adult age

Cardiac volumes by equilibrium gated cardiac blood pool scans and heart rate were measured in the supine and sitting positions in 64 male volunteer subjects (age 25-80 yrs) who had been rigorously screened to exclude cardiovascular disease. After the upright position was assumed, the average cardiac output of all subjects was unchanged but heart rate increased and stroke volume decreased due to a decrease in end diastolic volume. Neither the supine or sitting cardiac output nor the average postural change in cardiac output, cardiac volumes or heart rate was age-related. While the average cardiac output among the subjects was unaltered with a change in posture, in some individuals it increased slightly while in others it decreased. The postural change in cardiac output among the individuals correlated by linear regression analysis with a change in heart rate only in younger subjects and with a change in stroke volume in all age groups, but the slope of this relationship was greater in older than in younger subjects. The postural change in stroke volume was strongly correlated with a change in end diastolic volume and this relationship did not vary with age. Thus, although the average postural change in cardiac output among healthy subjects is not age-related, a given change in cardiac output with posture in an older individual depends more on a change in stroke volume and less on a heart rate change than in a younger one. This result, like the response to vigorous upright exercise previously demonstrated to occur with aging, indicates a greater reliance in the elderly on the Frank-Starling mechanism than on heart rate for a given change in cardiac output in response to perturbations from the basal supine state.

Age-related augmentation of plasma catecholamines during dynamic exercise in healthy males

Although plasma norepinephrine (NE) increases with age in response to a variety of submaximal adrenergic stimuli, the effect of age on plasma catecholamine levels during maximal aerobic effort and during submaximal work at a fixed percent of peak O2 consumption (VO2) is unknown. We therefore measured NE, epinephrine (E), and VO2 at rest and during graded maximal treadmill exercise in 24 healthy male volunteers (ages 22-77 yr) from the Baltimore Longitudinal Study of Aging who were rigorously screened to exclude the presence of cardiovascular disease. At rest neither heart rate (HR) nor VO2 were age related. Resting NE (pg/ml) was not age related, but resting E (pg/ml) was higher in male subjects 68-77 yr old (group III) than in those aged 22-37 (group I) or 44-55 yr (group II), P less than 0.01. Maximal HR (beats/min) showed a strong inverse relationship to age (203.5 - 0.65 age, r = -0.80, P less than 0.001). Peak VO2 in milliliters per kilogram total body weight per minute decreased with age (47.7 - 0.23 age, r = -0.71, P less than 0.001). At maximal effort both NE (P less than 0.01) and E (P less than 0.05) were higher in group III than in either of the younger groups. At submaximal work levels NE and E also increased with age, and when normalized for relative effort at loads between 45 and 80% of peak VO2 both NE and E were higher in the group III male subjects, although statistical significance was reached for NE (P less than 0.01) but not for E (P = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence and prognosis of exercise-induced nonsustained ventricular tachycardia in apparently healthy volunteers

Although exercise-induced ventricular tachycardia (VT), whether sustained or nonsustained, is usually associated with significant organic heart disease, its prevalence, associated characteristics and prognostic significance in an asymptomatic, unreferred community-dwelling population are unknown. Therefore, the prevalence of VT associated with maximal treadmill exercise was assessed in 597 male and 325 female volunteers, aged 21 to 96 years (mean +/- standard deviation 54 +/- 16), from the Baltimore Longitudinal Study on Aging who were without apparent heart disease. Ten subjects, 7 men and 3 women, with exercise-induced VT were identified, representing 1.1% of those tested; only 1 was younger than 65 years. All episodes of VT were asymptomatic and nonsustained. In 9 of 10 subjects, VT developed at or near peak exercise. The longest run of VT was 6 beats; multiple runs of VT were present in 4 subjects. Two subjects had exercise-induced ST-segment depression, but subsequent exercise thallium scintigraphic results were negative in each. Compared with a group of age- and sex-matched control subjects, those with asymptomatic, nonsustained VT displayed no difference in exercise duration, maximal heart rate, or the prevalence of coronary risk factors or exercise-induced ischemia as measured by electrocardiography and thallium scintigraphy. Over a mean follow-up period of 2 years, no subject has developed symptoms of heart disease or experienced syncope or sudden death. Thus, exercise-induced VT in apparently healthy subjects occurs almost exclusively in the elderly, is limited to short, asymptomatic runs of 3 to 6 beats usually near peak exercise, and does not portend increased cardiovascular morbidity or mortality rates over a 2-year period of observation.

Insensitivity of the electrocardiogram in apical myocardial infarction

The ability of the standard ECG to identify myocardial infarction (MI) involving primarily the left ventricular (LV) apex is controversial. Therefore, the ECGs of 62 consecutive patients with acute infarction and isolated akinesia or dyskinesia of the LV apex on gated blood pool scintigraphy performed at rest 9 +/- 4 days after MI, were reviewed. The following distribution of Q waves was found: none, 26%; inferior leads only, 23%; anterior leads only, 32%; inferior + 1 or more V leads, 13%; lead I and/or aVL + 1 or more V leads, 6%. Only 12 patients (19%) demonstrated one of the "combination" Q-wave patterns thought to indicate apical infarction. Although the 20 patients with a history of MI did not differ in age or ejection fraction from those with a first MI, the combination of inferior and anterior Q waves was present in 6 of them (30%), vs only 2 of the remaining 42 patients (5%) (p less than 0.02). The 24 patients with apical dyskinesia had a lower ejection fraction (36 +/- 14 vs 48 +/- 12, p less than 0.001), a lower prevalence of isolated inferior Q waves (8 vs 32%, p less than 0.05) and a greater prevalence of isolated anterior Q waves (46 vs 24%, p = 0.09) than those with akinesia. Thus, in patients with recent MI localized to the LV apex on radionuclide ventriculography, pathologic Q waves are commonly confined to the anterior or inferior leads or absent altogether. The insensitivity of the various proposed criteria for the electrocardiographic diagnosis of apical MI emphasizes the value of imaging techniques in detecting this common clinical entity.

Exercise cardiac output is maintained with advancing age in healthy human subjects: cardiac dilatation and increased stroke volume compensate for a diminished heart rate

To assess the effect of age on cardiac volumes and function in the absence of overt or occult coronary disease, we performed serial gated blood pool scans at rest and during progressive upright bicycle exercise to exhaustion in 61 participants in the Baltimore Longitudinal Study of Aging. The subjects ranged in age from 25 to 79 years and were free of cardiac disease according to their histories and results of physical, resting and stress electrocardiographic, and stress thallium scintigraphic examinations. Absolute left ventricular volumes were obtained at each workload. There were no age-related changes in cardiac output, end-diastolic or end-systolic volumes, or ejection fraction at rest. During vigorous exercise (125 W), cardiac output was not related to age (cardiac output [1/min] = 16.02 + 0.03 [age]; r = .12, p = .46). However, there was an age-related increase in end-diastolic volume (end-diastolic volume [ml] = 86.30 + 1.48 [age]; r = .47, p = .003) and stroke volume (stroke volume [ml] = 85.52 + 0.80 [age]; r = .37, p = .02), and an age-related decrease in heart rate (heart rate [beats/min] = 184.66 - 0.70 [age]; r = -.50, p = .002). The dependence of the age-related increase in stroke volume on diastolic filling was emphasized by the fact that at this high workload end-systolic volume was higher (end-systolic volume [ml] = 3.09 + 0.65 [age]; r = .45, p = .003) and ejection fraction lower (ejection fraction = 88.48 - 0.18 [age]; r = -.33, p = .04) with increasing age. These findings indicate that although aging does not limit cardiac output per se in healthy community-dwelling subjects, the hemodynamic profile accompanying exercise is altered by age and can be explained by an age-related diminution in the cardiovascular response to beta-adrenergic stimulation.

Asystole following treadmill exercise in a man without organic heart disease

A 52-year-old man without evidence of organic heart disease by clinical and extensive noninvasive examination experienced an 11-s episode of asystole ten minutes after completing a maximal treadmill test. Four years previously, symptomatic sinus bradycardia and hypotension had also followed cessation of treadmill exercise. This case illustrates that vagally mediated complications of treadmill exercise occurring in persons without apparent heart disease may be potentially life-threatening and can be elicited on repeated testing.

Longitudinal chest x-ray changes in normal men

To determine the changes on chest x-ray attributable to the aging process, we evaluated cardiovascular and pulmonary structures on two standard postero-anterior chest x-rays taken at least 10 years apart (M = 16.9 years) in 67 carefully screened healthy men initially aged 23 to 76 years. The aortic knob diameter increased in 79% of subjects. Although mean cardiothoracic ratio increased overall, only 3% of men developed a cardiothoracic ratio greater than .50, and none exceeded .51. Pulmonary abnormalities on initial chest x-ray consisted mainly of hyperinflation (27%) and increased markings (19%), both of which doubled in prevalence during follow-up. Kerley B lines and enlarged pulmonary arteries were rare initially but increased three- to five-fold. The prevalence of these findings did not differ between smokers and nonsmokers. Based on commonly accepted x-ray criteria, chronic obstructive lung disease was suggested in 15% of the initial films and 21% of the final films despite the absence of clinical or spirometric abnormalities.

Right bundle branch block: long-term prognosis in apparently healthy men

The long-term cardiac prognosis of 24 clinically healthy men with complete right bundle branch block, identified from the 1,142 men constituting the population of the Baltimore Longitudinal Study on Aging, was assessed over a follow-up period averaging 8.4 years. When compared with a control group matched for age at which right bundle branch block appeared (mean +/- standard deviation 64.0 +/- 13.5 years), men with right bundle branch block showed no difference in the prevalence of antecedent coronary risk factors or obstructive lung disease. The incidence of angina pectoris, myocardial infarction, valvular heart disease, cardiomegaly, congestive heart failure, advanced heart block or cardiac death in these men did not differ from that of the control group over the observation period. Furthermore, at the latest follow-up study, maximal aerobic exercise tolerance and chronotropic response to maximal exercise were not impaired in men with right bundle branch block relative to control men (9.1 +/- 2.2 versus 7.3 +/- 3.0 minutes and 150.3 +/- 23.5 versus 147.7 +/- 20.7 beats/minute, respectively). However, axis deviation leftward of -30 degrees was present in 46% of men with right bundle branch block but in only 15% of control subjects at latest follow-up (probability [p] less than 0.01). Although the PR interval lengthened by 40 ms or more developed in only 6% of control subjects over the observation period, such prolongation occurred in 29% of men with right bundle branch block (p less than 0.05). These results support the concept that right bundle branch block in these asymptomatic men is a manifestation of a primary abnormality of the cardiac conduction system but has no demonstrable adverse effect on long-term cardiac morbidity or mortality.

Is digoxin really important in treatment of compensated heart failure? A placebo-controlled crossover study in patients with sinus rhythm

To assess the efficacy of digitalis in patients with chronic clinically compensated congestive heart failure and normal sinus rhythm, we performed a double-blind crossover study with digoxin and placebo in 30 consecutive outpatients fulfilling these criteria; serum digoxin levels, clinical symptoms and signs, and objective indexes of cardiac function were monitored. No patient's clinical condition deteriorated during three months of placebo administration. Discontinuation of digoxin resulted in a small increase in echocardiographically determined resting left ventricular end-diastolic dimension (1.8 +/- 0.6 mm, p less than 0.001) and a similar decrease in velocity of circumferential fiber shortening (-0.08 +/- 0.04 circ/sec, p less than 0.05) from the corresponding values of 55.8 +/- 2.3 mm and 0.90 +/- 0.08 circ/sec during digitalis therapy. Resting left ventricular ejection time and pre-ejection period were prolonged by digoxin withdrawal. Maximal exercise capacity was unchanged. No clinical exacerbation of heart failure attributable to digitalis withdrawal occurred over a follow-up period averaging 19 months. The results indicate that long-term digoxin therapy has only a minor effect on cardiac performance that is without apparent clinical importance in a representative population of ambulatory patients treated with cardiac glycosides.

Cardiac arrhythmias in a healthy elderly population: detection by 24-hour ambulatory electrocardiography

Twenty-four hour ambulatory electrocardiographic examination was preformed in 98 healthy active subjects, ages 60 to 85 years, who were participants in a longitudinal study on aging. Normal health was confirmed by noninvasive testing, including maximal treadmill exercise (98/98) and thallium scintigraphy (38/98). Our studies indicated that a healthy population of elderly subjects shows a substantial prevalence of supraventricular ectopic beats and ventricular ectopic beats, both isolated and complex. High degree AV block, profound sinus bradycardia, abnormal sinus pauses and sinus arrest are rare in normal elderly subjects.

99mTc-pyrophosphate imaging in acute pericarditis: a clinical and experimental study

Fifteen patients with clinical and electrocardiographic features of acute pericarditis underwent myocardial scintigraphy using 99mTc-pyrophosphate. All had normal images. In 5 additional patients with acute pericarditis and evidence of ischemic heart disease, 99mTc-pyrophosphate images showed focal abnormalities in 2 patients and equivocal findings in 2. Serial myocardial radionuclide images were obtained 2 to 18 days after induction of pericarditis in 8 dogs; all images were normal. No stainable tissue calcium was demonstrated histochemically in the pericardium or myocardium of these dogs. Our results suggest that 99mTc-PYP myocardial radionuclide images are normal in acute pericarditis in the absence of ischemic heart disease.