Comparison of cardiovascular response to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone in patients with chronic ischemic heart disease

The cardiovascular risks of physical activity

The incidence of sudden death, serious arrhythmias, and myocardial infarction in connection with both recreational and rehabilitative physical activity is small. However, the incidence of e.g. sudden death is several times higher in exercise than at other times. This relative risk is highest in middle-aged men, and higher in strenuous than in nonstrenuous exercise. In the vast majority of the cases the underlying cause is advanced coronary heart disease, which in large proportion of the cases has been asymptomatic and has allowed regular strenuous training. Attempts to prevent the complications by special large scale screening programs would be ineffective and individual counselling limited by lack of resources. These measures should, however, be used in selected groups and individuals. Another approach is to inform the exercisers and their families at large by systematic, well-planned and repeated messages of the risks of physical activity, of the symptoms and findings indicating this risk, of the individual and environmental factors increasing the risk, and of the necessary measures to be taken to minimize the risk. Even if all available measures at present were used, the cardiovascular complications of physical activity could not be totally prevented. Fortunately, preliminary evidence suggests that at population level the cardiovascular hazards of physical activity are outweighed by its cardiovascular benefits.

Resistance Exercise Training in Patients with Heart Failure

The utility, safety and physiological adaptations of resistance exercise training in patients with chronic heart failure (CHF) are reviewed and recommendations based on current research are presented. Patients with CHF have a poor clinical status and impaired exercise capacity due to both cardiac limitations and peripheral maladaptations of the skeletal musculature. Because muscle atrophy has been demonstrated to be a hallmark of CHF, the main principle of exercise programmes in such patients is to train the peripheral muscles effectively without producing great cardiovascular stress. For this reason, new modes of training as well as new training methods have been applied. Dynamic resistance training, based on the principles of interval training, has recently been established as a safe and effective mode of exercise in patients with CHF. Patients perform dynamic strength exercises slowly, on specific machines at an intensity usually in the range of 50-60% of one repetition maximum; work phases are of short duration (< or =60 seconds) and should be followed by an adequate recovery period (work/recovery ratio >1 : 2). Patients with a low cardiac reserve can use small free weights (0.5, 1 or 3 kg), elastic bands with 8-10 repetitions, or they can perform resistance exercises in a segmental fashion. Based on recent scientific evidence, the application of specific resistance exercise programmes is safe and induces significant histochemical, metabolic and functional adaptations in skeletal muscles, contributing to the treatment of muscle weakness and specific myopathy occurring in the majority of CHF patients. Increased exercise tolerance and peak oxygen consumption (V-dotO(2peak)), changes in muscle composition, increases in muscle mass, alterations in skeletal muscle metabolism, improvement in muscular strength and endurance have also been reported in the literature after resistance exercise alone or in combination with aerobic exercise. According to new scientific evidence, appropriate dynamic resistance exercise should be recommended as a safe and effective alternative training mode (supplementary to conventional aerobic exercise) in order to counteract peripheral maladaptation and improve muscle strength, which is necessary for recreational and daily living activities, and thus quality of life, of patients with stable, CHF.

Cardiovascular response to combined static-dynamic exercise of patients with myocardial infarction

BACKGROUND

Graded dynamic exercise-stress testing of patients with acute myocardial infarction prior to discharge from hospital has an important diagnostic and prognostic implication. Although many daily tasks involve combinations of static and dynamic exercise, little is known about cardiovascular responses during combined static-dynamic exercise.

OBJECTIVE

To determine the difference between cardiovascular responses during two types of combined static-dynamic exercise (a 10 kg weight in one hand, and a 10 kg weight bearing on the shoulder).

METHODS

We studied 27 male patients who had recently suffered myocardial infarction using ear densitography. The patients were divided into two groups: group 1 was comprised of 14 patients with resting left ventricular end-diastolic volumes > or = 140 ml, and group 2 was comprised of 13 patients with left ventricular end-diastolic volumes < 140 ml.

RESULTS

For eight patients in group 1 we detected positive electrocardiographic changes during one-hand weight-carrying exercise, but for none of these patients was there an electrocardiographic change during weight-bearing exercise. All the patients in group 2 completed both types of exercise without significant ST-segment change. Although there were no significant differences between values of any of the indices measured for the two groups during weight-bearing exercise, patients in group 1 had significantly shorter diastolic times/min (21.8 +/- 2.1 versus 25.1 +/- 2.4 s/min, P < 0.01) during one-hand weight carrying.

CONCLUSIONS

In addition to decrease in subendocardial coronary blood flow associated with increase in left ventricular end-diastolic volume, shortening of diastolic perfusion time during one-hand weight-carrying exercise for patients in group 1 can potentially contribute to subendocardial ischemia, which was favorably altered by bearing a weight on the shoulder.

Fasting and postprandial ischemic threshold in patients with unstable angina with and without postprandial angina at rest

BACKGROUND

Postprandial angina develops within minutes after a meal in patients with unstable angina, but the clinical characteristics of these patients and why it develops in only some of those with advanced coronary artery disease remain largely unknown. A severely reduced coronary reserve associated with postprandial increases in heart rate could be a contributory mechanism.

METHODS

The clinical and angiographic characteristics of 277 patients with unstable angina with (23) or without (254) postprandial angina were analyzed. The coronary reserve was also analyzed by measuring the ischemic threshold by atrial pacing in a fasting state in all patients and 15 minutes after a 900-calorie meal in 54.

RESULTS

Patients with postprandial angina were older, more likely to be women, and had a higher incidence of hypertension and three-vessel disease than those without (p < 0.005) and had a lower fasting ischemic threshold (131.8 [SD 13.0] vs 147.5 [SD 23.4] beats/min, p < 0.0001). However, 67 of the 79 patients with the lowest fasting thresholds (< or =130 beats/min) (84.8%) had no postprandial angina. Moreover, among patients with and without postprandial angina who were matched for age, sex, and extent of coronary disease, the ischemic threshold was also lower in those with postprandial angina (p < 0.005) and there were no differences in left ventricular end-diastolic pressure or volume. Postprandial pacing was positive in 37 patients but postprandial ischemic threshold was comparable to fasting threshold (132 [SD 14] vs 132 [SD 16] beats/min). Moreover, in the 10 patients who experienced in-hospital postprandial angina, heart rate during postprandial angina was similar to nonpostprandial angina (93.1 [SD 14.7] vs 90.3 [SD 17.6]) and lower than the fasting ischemic threshold (132.0 [SD 10.8] beats/min, p < 0.0001).

CONCLUSIONS

Thus postprandial angina tends to occur among elderly and hypertensive patients with advanced coronary disease and severely reduced ischemic threshold. The fact that the postprandial ischemic threshold was clearly higher than the heart rate attained during postprandial angina suggest that factors others than increases in heart rate account for postprandial angina. Furthermore, the lack of a decline in the postprandial ischemic threshold suggests that, in the absence of postprandial angina, there is not a consistent postprandial change in coronary tone or that the increases in myocardial oxygen demands due to increased myocardial contractility-wall tension do not seem to play a major role in postprandial ischemia.

A controlled trial of circuit weight training on aerobic capacity and myocardial oxygen demand in men after coronary artery bypass surgery

BACKGROUND

Cardiovascular benefits of resistance training in cardiac patients have been suggested but not studied in a randomized, controlled trial of circuit weight training (CWT) without an aerobic exercise component. The purpose of the current study was to examine the effects of 10 weeks of CWT on muscular strength, peak oxygen consumption (peak VO2), and myocardial oxygen demand (mVO2) in men after coronary artery bypass surgery.

METHODS

Twenty-six, post-coronary bypass male subjects (mean 19 months after bypass), aged 60 +/- 8.5 years, were randomly allocated to 10 weeks of CWT at 40 to 60% of maximum voluntary contraction (n = 12) or to a control group (n = 14). Muscular strength was assessed using a modified one repetition maximum technique. Peak VO2 was recorded during symptom-limited treadmill exercise. Rate pressure product, as an indirect measure of mVO2, was measured during isometric, isodynamic, and dynamic exercise.

RESULTS

No ischemic symptoms nor electrocardiographic changes were recorded during testing or training. Strength increased by 18% (P < 0.005) in five out of seven exercises in the training group, but was unchanged in the control group. Training did not improve peak VO2. Rate pressure product during isometric and isodynamic exercise decreased from pre- to post-testing (P < 0.05) but was equivalent to that seen in the control group.

CONCLUSIONS

Moderate intensity CWT is safe and can improve strength in selected low-risk patients after coronary artery bypass surgery. However, it does not significantly increase peak VO2 nor reduce mVO2 during isometric, isodynamic, and dynamic exercise.

Cardiac rehabilitation: potential for ergonomic interventions with special reference to return to work and the Americans with Disabilities Act

This paper briefly reviews the contemporary cardiac rehabilitation process and highlights its limitations. It argues that, in order to improve return-to-work chances, cardiac rehabilitation should focus on simulating actual work conditions. The role of ergonomics in the cardiac rehabilitation process is also outlined. Finally, the current impediments to early return to work are identified and corrective actions are suggested.

Weight carrying effects on treadmill exercise response in persons without heart disease

To evaluate the effect of weight carrying on dynamic exercise response, 12 normal subjects were studied during treadmill exercise using ear densitography in two ways: (1) no weight, (2) 10 kg weight in one hand. Although there were no significant differences in diastolic time (DT), tension-time index [TTI: systolic blood pressure x heart rate (HR) x left ventricular ejection time (LVET)] was significantly higher throughout the weight carrying exercise compared to dynamic exercise. The amount of change (delta) in TTI was significantly larger in the initial stage (control to 1 min) of weight carrying exercise compared to dynamic exercise, but there were no significant differences in the later stages (1-3 min and 3-6 min). A prolongation in LVET was observed despite increasing HR during the first minute of exercise in both type of exercise, but LVET was longer at any given HR in weight carrying compared to dynamic exercise. Thus, despite higher TTI throughout the weight carrying exercise, delta TTI was larger only in the initial stage which was caused by prolongation of LVET resulting from disproportionate increase in venous return of early exercise.

Effect of a standardized meal on the threshold of exercise-induced myocardial ischemia in patients with stable angina

OBJECTIVES

This study was undertaken to determine the effect of a standardized meal on the ischemic threshold and exercise capacity in a series of 20 patients with stable angina, exercise-induced ischemia and reversible exercise-induced perfusion defects.

BACKGROUND

It is generally accepted that exercise tolerance in patients with angina is reduced after a meal. However, studies that have addressed this phenomenon have yielded results that are contradictory and inconclusive.

METHODS

Two exercise tests using the Bruce protocol with technetium-99m (99mTc)-sestamibi were performed on consecutive days in a randomized order. One test was performed in the fasting state and the other 30 min after a 1,000-calorie meal.

RESULTS

In the postprandial state, exercise time to ischemia was reduced by 20% from 248 +/- 93 s to 197 +/- 87 s (p = 0.0007), time to angina by 15% from 340 +/- 82 s to 287 +/- 94 s (p = 0.002) and exercise tolerance by 9% from 376 +/- 65 s to 344 +/- 86 s (p = 0.002). Rate-pressure products at these exercise test end points were not significantly different in the fasting and postprandial tests, and the quantitative 99mTc-sestamibi ischemia score was unchanged.

CONCLUSIONS

In patients with stable angina, a 1,000-calorie meal significantly reduced time to ischemia, time to angina and exercise tolerance because of a more rapid increase in myocardial oxygen demand with exercise. The extent and severity of exercise-induced ischemia were unchanged.

Usefulness of heavy isometric exercise echocardiography for assessing left ventricular wall motion patterns late (> or = 6 months) after acute myocardial infarction

The aim of this prospective study was to determine the effects of heavy isometric exercise on left ventricular (LV) wall motion patterns in patients who have had myocardial infarction, and to compare heavy isometric exercise with dynamic exercise for competence in eliciting LV wall motion abnormalities at equivalent rate-pressure products. Echocardiography was performed in 42 patients during supine bicycle ergometry and during heavy dynamometer stretching at 50% of maximal voluntary contraction. Systemic vascular resistance increased from 1,484 to 1,649 dynes s cm-5 (p < 0.05) during isometric exercise, and decreased significantly during dynamic exercise. Wall motion abnormalities or new asynergy were induced by isometric exercise in 120 segments, 107 of which (89%) showed significant stenosis of the perfusing coronary artery. Hypokinesia was the dominant pattern in the range of 76 to 90% narrowing; akinesia was dominant at 91 to 100% narrowing. Wall motion abnormalities were also documented in 13 segments (11%) assumed to be supplied by vessels with nonsignificant stenosis. Dyskinesia, seen in 7% of the segments, was equally distributed between both groups with significant stenosis. Sensitivity and positive predictive value in identifying specific coronary vessel disease was similar for both isometric and dynamic exercise. In conclusion, heavy isometric exercise in patients who have had myocardial infarction induces wall motion abnormalities of a severity proportional to the degree of coronary narrowing. This exercise method is similar to dynamic exercise for ability in identifying obstructions in a specific vessel. Furthermore, when compared at near-equal rate-pressure products, heavy isometric exercise is far superior in sensitivity to dynamic exercise.

Weight carrying versus handgrip exercise testing in men with coronary artery disease

The clinical merits of handgrip and weight carrying tests were compared in 30 patients with documented coronary artery disease. The static loads in the 2 tests were matched by percentage of maximal static effort and corresponded to 25 and 45% of maximal voluntary handgrip contraction and 25 and 45% of maximal 1-hand lift capacity. Each static load in both tests was continued for less than or equal to 3 minutes. At the 25% maximal effort stage, 93 and 90% of patients were able to complete 3 minutes of handgrip and weight carrying, respectively. Only 13 and 10% were able to complete 3 minutes at the 45% maximal effort stage with handgrip and weight carrying, respectively. Arm fatigue and an increase in diastolic blood pressure greater than 120 mm Hg were the predominant endpoints. Weight carrying resulted in significantly higher (p less than 0.05) heart rate, systolic blood pressure, pressure-rate product, ventilation and oxygen consumption compared to handgrip. Diastolic blood pressure responses did not differ between the tests. None of the patients demonstrated ischemic responses to either handgrip or weight carrying and the incidence of arrhythmias was rare. The diastolic blood pressure response to static effort is equally evaluated by handgrip and weight carrying tests. However, the greater myocardial oxygen demand, reflected by the pressure-rate product, in addition to the greater total body oxygen consumption, imposed by weight carrying, enhances the clinical application of the weight carrying test.

The safety of static-dynamic effort soon after myocardial infarction

Many activities of daily living require static-dynamic effort. To evaluate the safety of such effort 3 weeks after myocardial infarction, 27 male patients underwent a weight-carrying test requiring 5 minutes of treadmill ambulation with graded weight loads of 10 to 30 pounds. The hemodynamic responses with weight carrying were compared to that of a predischarge graded dynamic exercise test. The peak heart rate was significantly lower (p less than 0.01) with weight carrying, the peak systolic blood pressure did not differ, and the diastolic pressure was significantly higher (P less than 0.01). ST segment depression and angina pectoris occurred less frequently with weight carrying. The type and frequency of ventricular arrhythmias were similar between the two tests. We conclude that many men are capable of performing static-dynamic activity equivalent to carrying up to 30 pounds by 3 weeks after myocardial infarction.

Exercise testing to enhance wives' confidence in their husbands' cardiac capability soon after clinically uncomplicated acute myocardial infarction

The effects of wives' involvement in their husbands' performance of treadmill exercise testing 3 weeks after clinically uncomplicated acute myocardial infarction was compared in 10 wives who did not observe the test, 10 who observed the test, and 10 who observed and participated in the test themselves. In a counseling session after the treadmill test, couples were fully informed about the patient's capacity to perform various physical activities. Wives' final ratings of confidence (perceived efficacy) in their husbands' physical and cardiac capability were significantly (p less than 0.05) higher in those who also performed the test than in the other 2 groups. Only wives who walked on the treadmill increased their ratings of their husbands' physical and cardiac efficacy to a level equivalent to those of their husbands. Spouses' and patients' perceptions of patients' cardiac capability after treadmill testing and counseling at 3 weeks were significantly correlated with peak treadmill heart rate and workload at 11 and 26 weeks. Efficacy ratings at 3 weeks were slightly better than peak 3-week treadmill heart rate and workload as predictors of treadmill performance at 11 and 26 weeks. Participation in treadmill testing early after acute myocardial infarction is an effective means for reassuring spouses about the capacity of their partners to resume their customary physical activities with safety.

Myocardial ischaemia during daily life in patients with stable angina: its relation to symptoms and heart rate changes

In thirty patients with stable angina and positive exercise tests, ambulatory ST segment monitoring was used to record episodes of transient myocardial ischaemia during daily life. All patients had four consecutive days of monitoring and in 20 patients long-term variability was assessed by repeated 48 hour monitoring and exercise testing over 18 months. There were 1934 episodes of rectilinear or downsloping ST-depression (911, 1 mm; 638, 2 mm; 385, greater than 3 mm) in 446 days of recording, of which only 470 (24%) were accompanied by angina. Positron tomography showed evidence of regional myocardial ischaemia during both symptomatic and asymptomatic ST depression. On average, heart rate at the onset of both symptomatic and asymptomatic ST episodes was significantly lower than the rate at the onset of ST depression during exercise testing (98 +/- 20.5 vs 124 +/- 17 beats/minute). Heart rate rose by more than 10 beats in the minute preceding ST depression in only 23% of episodes. Over 18 months, 8 (40%) patients exhibited marked variability in the number of daily ST episodes. Variability of ST depression was consistently underestimated by symptoms and not reflected by exercise testing. Thus, patients with stable angina showed frequent, variable, and often asymptomatic electrocardiographic evidence of ischaemia. Heart rate increase was not common before myocardial ischaemia, suggesting that, in such patients, transient impairment in coronary supply may be at least as important as excessive increase in demand in the genesis of ischaemia during daily life.

Response of patients after myocardial infarction to carrying a graded series of weight loads

Cardiovascular responses to carrying graded weight loads of 20 to 50 pounds were determined in 52 patients after myocardial infarction (MI) (greater than or equal to 2 months). Sixty percent of the patients were stopped before completing the heaviest weight load (50 pounds for 2 minutes) because of an increase in diastolic blood pressure (BP) to 120 mm Hg (end point) or arm fatigue. Compared with symptom-limited graded dynamic exercise, peak systolic and diastolic BP were significantly greater (p less than 0.05 and p less than 0.01, respectively) with weight carrying, while peak heart rate, pressure-rate product, ventilation and oxygen consumption were significantly lower (p less than 0.01). Ischemic responses were less frequent with weight carrying. Patients with severely reduced resting left ventricular ejection fraction (LVEF) (less than 35%) tolerated the weight carrying test as well as patients with normal resting LVEFs (greater than 50%). We conclude that (1) ischemic responses occur less frequently while carrying up to 50 pounds for 2 minutes than with symptom-limited dynamic exercise, (2) a significant number of patients have an increase in diastolic BP greater than or equal to 120 mm Hg while carrying objects that weigh 30 to 50 pounds for 2 minutes, and (3) a poor correlation exists between resting LVEF and tolerance for weight carrying.