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PubMed1983

Value of isometric exercise testing during cardiac catheterization in mitral stenosis.

To examine the value of preoperative isometric exercise testing during cardiac catheterization in patients with mitral stenosis, the isometric handgrip exercise test was performed on 28 patients during preoperative diagnostic catheterization. Eighteen patients who subsequently underwent mitral valve surgery were recatheterized and reevaluated clinically 12 months after operation. Preoperatively, the patients were divided into 2 groups: 16 whose mean mitral valve pressure gradient increased greater than 4 mm Hg during isometric exercise (group A) and 12 whose pressure gradient decreased or increased less than 4 mm Hg (group B). The ejection fraction remained unchanged and the peak systolic pressure/end-systolic volume ratio increased during isometric exercise in group A (p less than 0.001). In group B, the ejection fraction decreased (p less than 0.001) and the peak systolic pressure/end-systolic volume ratio remained unchanged. In the total group, a positive correlation existed between the change in mean mitral valve pressure gradient during isometric exercise and the changes in measures of left ventricular function during exercise. The patients in group A had a significant improvement in both symptoms and in exercise tolerance as determined by symptom-limited bicycle ergometry after surgery. The patients in group B showed minimal or no symptomatic improvement and their exercise tolerance did not improve. The change in mitral valve pressure gradient during isometric exercise appears to reflect the left ventricular response to exercise.

Adult↗

PubMed1985

Maximal work capacity in prepubescent obese and nonobese females.

Measurements of cardiorespiratory function during an incremental treadmill test were compared in 15 obese (OB) prepubescent girls, 7 to 12 years old, and in 15 age-matched, nonobese (NOB) controls. Open circuit calorimetry was used for data collection during the progressive work test. Maximal oxygen consumption indexed for weight was significantly lower in the obese group of girls (23.0 +/- 3.9 ml/kg/min) than in the nonobese controls (36.7 +/- 0.9 ml/kg/min). In addition, exercise tolerance was longer in the nonobese group, albeit not statistically significant. In conclusion, diminished cardiopulmonary performance and attenuated exercise tolerance in prepubescent obese females in the current investigation seemed to be influenced by excess body weight.

Body Height↗

PubMed1991

Inhibition of dipyridamole-induced ischemia by antianginal therapy in humans. Correlation with exercise electrocardiography.

BACKGROUND: Dipyridamole echocardiography test (DET: two-dimensional echocardiographic monitoring with dipyridamole infusion up to 0.84 mg/kg in 10 minutes) is a useful tool for the noninvasive diagnosis of coronary artery disease. Aims of the present study were to assess the effects of antianginal drugs on dipyridamole-induced ischemia and to evaluate whether drug-induced changes in DET response may predict variations in exercise tolerance. METHODS AND RESULTS: Fifty-seven patients with angiographically assessed significant coronary artery disease (greater than 70% lumen reduction in at least one major coronary vessel) performed a DET and an exercise electrocardiography test (EET) in random order both off treatment and on antianginal drugs (beta-blockers, calcium antagonists and nitrates, alone or in various combinations). The criterion for DET positivity was a transient dyssynergy of contraction absent or of a lesser degree in the baseline examination. In DET, two parameters were evaluated: the dipyridamole time (i.e., the time from onset of dipyridamole infusion to obvious dyssynergy) and the wall motion score index. DET sensitivity was 91% off therapy and fell to 65% under therapy (p less than 0.01). In the 37 patients who had a positive DET both off and on therapy, the dipyridamole time increased from 6 +/- 3 (off therapy) to 8 +/- 3 minutes (on therapy) (p less than 0.01). The wall motion score index at peak dipyridamole went from 1.38 +/- 0.14 to 1.31 +/- 0.14 (p less than 0.01). EET and DET yielded concordant (positive versus negative) results in 41 of 57 (71%) patients off and in 35 of 57 (61%) on therapy (p = NS). In the subgroup of 38 patients with both positive DET and EET without treatment, the therapy-induced variations in exercise time were significantly correlated with the variations in dipyridamole time (r = 0.5; p less than 0.01), not with variations in wall motion score index (r = 0.3; p = NS). CONCLUSIONS: 1) Antianginal therapy can protect from dipyridamole-induced ischemia and 2) the therapy-induced changes in DET response parallel variations in exercise tolerance and might be useful for the objective, exercise-independent assessment of the therapy efficacy.

Adrenergic beta-Antagonists↗

PubMed1989

Improvement in maximal isokinetic cycle ergometry with cardiac rehabilitation.

It is unclear whether improvements in short-term (30 s) exercise capacity are associated with the increased aerobic exercise tolerance frequently observed in cardiac patients following training. Carefully selected patients with documented coronary artery disease were randomly allocated either to a control group (N = 10) or to 12 wk of endurance exercise training (N = 12); both progressive incremental cycle ergometer testing (maximal power output and peak VO2) and 30 s maximal isokinetic cycle ergometry (peak power, total work, and fatigue index) were measured on entry into the study and 12 wk later. Initial maximum performance measures in progressive incremental exercise and in maximal short-term isokinetic cycling were similar in both groups. Following the training program, maximum power output measured during progressive incremental exercise increased by 21% (P less than 0.005) and peak VO2 increased by 18% (P less than 0.005) in the exercise group, but they were unchanged in the control group. Isokinetic peak power and total work improved by 14% (P less than 0.001) and 11%, respectively, in the exercise group, whereas there were corresponding reductions of 6 and 8% in the control subjects, with little change in fatigue index in either group. The similar relative increases in isokinetic peak power and peak VO2 suggest that improvement in short-term exercise capacity may be an important contributor to the improvement in aerobic exercise tolerance frequently observed in cardiac patients undergoing an endurance exercise program.

Coronary Disease↗

PubMed1995

Training increases collateral-dependent muscle blood flow in aged rats.

The potential for physical training to enhance collateral-dependent blood flow (BF) to the hindlimbs of aged male rats (Fischer 344) was evaluated following bilateral femoral artery ligation at 20.5 mo of age. Rats were either limited to cage activity (sedentary, n = 11) or trained by a mild-intensity treadmill program (trained, n = 14), which involved walking twice a day at 15 m/min (15% grade) to fatigue, 5 days/wk for 8-11 wk. Exercise tolerance of the trained rats increased from approximately 5 to approximately 25 min/bout by week 7, whereas exercise tolerance of the sedentary group changed little (to approximately 8 min/bout) during the training period. At approximately 23 mo age, animals were surgically prepared for hindquarter perfusion (aortic pressure = 100 +/- 1.3 mmHg) and force measurement of the left gastrocnemius-plantaris-soleus (GPS) muscle group during isometric contractions at 4, 8, 15, 30, and 45 tetani/min via sciatic nerve stimulation (approximately 6 V, 0.1-ms square waves at 100 Hz for 100 ms). Although initial force development was similar between groups (12.9 N/g), trained rats maintained tension better at 8, 15, 30, and 45 tetani/min (P < 0.01). BF to the entire hindlimb of the trained group, determined with 85Sr 15-microns microspheres, was 43% greater (P < 0.05) than in the sedentary group. Thus collateral-dependent BF was improved by physical training. The greatest increase in BF was to the distal limb muscles (approximately 78%), the tissues most at risk during intermittent claudication.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1990

Corticosteroids prevent early deterioration in patients with moderately severe Pneumocystis carinii pneumonia and the acquired immunodeficiency syndrome (AIDS)

OBJECTIVE: To determine whether oral corticosteroids can prevent early deterioration in patients with acquired immunodeficiency syndrome (AIDS)-related Pneumocystis carinii pneumonia. DESIGN: Prospective, double-blind, placebo-controlled, randomized trial. METHODS: Included patients were having their first P. carinii pneumonia episode, had no other known active pulmonary pathology, had no contraindications for corticosteroids, received no anti-P. carinii pneumonia medications for more than 48 hours, and had oxygen saturation by pulse oximetry of 85% or more and less than 90% at rest or a 5-percentage-point decrease in oxygen saturation with exercise while breathing room air. Consenting subjects were randomly assigned to prednisone, 60 mg/d for 7 days, followed by a progressive tapering over 14 days or to an identical placebo. Early deterioration, the endpoint of the trial, was defined as a 10% decrease in baseline oxygen saturation on day 3 or thereafter. The cases of patients developing early deterioration were considered to be failures of treatment; the code was then broken, and the patient's treatment was left to the judgment of the treating physician. Sequential analysis was done with the primary variable being development of early deterioration. RESULTS: The trial was terminated 5 April 1989 on the basis of the sequential analysis when a total of nine episodes of early deterioration had occurred in the first 37 patients at an overall significance level of P = 0.0136. A total of 8 of 19 placebo-treated patients (42.1%) developed early deterioration compared with only 1 of 18 patients (5.6%) treated with corticosteroids. Baseline characteristics were not statistically different between the two treatment groups. The adjusted odds ratio for the treatment effect was 5.87 (95% CI, 1.27 to 27.4). The adjusted point estimates for the probability of early deterioration in the placebo and corticosteroid groups were 43% and 12%, respectively. All 8 patients in the placebo group developing early deterioration recovered rapidly with addition of corticosteroid treatment. The single patient with early deterioration in the corticosteroid group died on day 6 from overwhelming P. carinii pneumonia, as documented at autopsy. The corticosteroid group had an increased exercise tolerance on day 7 that persisted at day 30. CONCLUSION: Oral corticosteroids prevent early deterioration and increase exercise tolerance in patients with moderately severe AIDS-related P. carinii pneumonia.

Acquired Immunodeficiency Syndrome↗

PubMed2001

[Effects of clinical indices and anti-angina therapy on the quality of life in patients with stable angina pectoris].

AIM: To determine effects of basic clinical indices and various antianginal drugs on quality of life (QL) assessed with general and special questionnaire before and after selection of antianginal therapy in patients with stable angina pectoris. MATERIAL AND METHODS: The study enrolled 89 patients with stable angina (functional class II-IV). They were examined before and after decision on adequate therapy. QL was assessed with questionnaires Disease Impact Profile and Seatle Angina Questionnaire (SAQ). Factors essential for QL were determined with factor analysis and multiple regression methods. QL correlation with exercise tolerance was examined. RESULTS: SAQ has identified a positive correlation of some parts and total QL with exercise tolerance (p < 0.05). Treatment satisfaction correlated negatively with intensity of threshold load (p < 0.05). Factors affecting QL differed in patients with selected and non-selected therapy. QL was affected by anginal severity and complications, concomitant diseases with chest pain, harmful habits. Intake of non-selected drugs (beta-adrenoblockers, aspirin, ACE inhibitors, saluretics, benzodiazepins) may deteriorate QL. CONCLUSION: It is impossible to describe QL with clinical characteristics alone. This is an independent index which requires a special estimation.

Adult↗

PubMed1989

Relationship between improvement in exercise performance with supplemental oxygen and hypoxic ventilatory drive in patients with chronic airflow obstruction.

The purpose of this study was to determine if there is a relationship between improvement in exercise capacity with supplemental oxygen and the magnitude of hypoxic ventilatory drive in patients with CAO. We hypothesized that those patients with the highest hypoxic drives would be the most likely to have increased exercise tolerance with supplemental oxygen. Seventeen patients with CAO (mean FEV1 = 0.99 +/- 0.45 L) underwent identical maximal cycle ergometry exercise tests on two occasions 45 minutes apart while breathing either air or 30 percent oxygen in a randomized single-blind fashion. With supplemental oxygen, the ventilation decreased and the PaCO2 increased significantly at rest. The patients had a significantly greater exercise tolerance on supplemental oxygen (76.7 vs 69.1 watts, p less than 0.005) but no increase in the maximal ventilation. When the nine patients who improved were compared to the eight patients who did not improve, the two groups were basically identical. Specifically, there were no significant differences in the mean ventilatory or mouth occlusion responses to hypoxia or in the blood gases. The patients who did improve tended to have a greater reduction in their ventilatory response to exercise while exercising on oxygen as compared to when they were exercising on room air. From this study, it was concluded that measurements of hypoxic ventilatory drive are not helpful in predicting which patients with CAO are likely to have improved exercise capability while breathing supplemental oxygen.

Aged↗

PubMed1993

[The development of tolerance to continuous transdermal nitroglycerin therapy in patients with angina of effort and mixed angina].

The present multicentre study, conducted in patients with angina pectoris on chronic therapy with continuous 24-hour transdermal nitroglycerin was aimed at investigating: (1) the actual incidence of nitrate tolerance; (2) the clinical features that characterize those who do not develop tolerance; (3) whether the evidence of clinical and ergometer benefits at 1-month assessment predicts their long-term maintenance. Eligible patients (n = 110; average age 56 +/- 5 yrs) had stable angina pectoris (78 effort angina, 32 mixed angina) with symptom-limited, reproducible cycloergometer tests and were responsive to s.l. nitroglycerin. After a 7-day washout period and a placebo run-in week, all patients were assigned to continuous 10 mg/24-hour nitroglycerin patches (T0). Exercise tests were performed again after 1 month (T1) and 6 months (T6) of treatment. At T1, ergometric data in each patient were compared with those at T0 and showed an increase (> or = 15%) in exercise tolerance in only 61/110 patients: 38 (49%; Group A) of the 78 patients with effort angina and 23 (72%; Group B) of the 32 patients with mixed angina (p < 0.05). Those patients with no significant change in exercise tolerance were assigned to conventional antianginal therapy and were excluded from the study. At T6, both group A and B patients maintained the favourable effects on total exercise duration, time and maximum workload at ischemic threshold and maximal ST depression recorded at T1 vs T0. The weekly attacks of angina and nitroglycerin s.I. consumption decreased significantly in both Group A and Group B patients from the beginning of therapy and throughout the study. These results show that: 1) tolerance to continuous 24-hour transdermal nitroglycerin therapy is not constant phenomenon, but occurs only in a subgroup of patients; 2) patients with mixed angina are more resistant to develop tolerance than those patients with effort angina; 3) the 1-month evidence of clinical and ergometric benefits predicts their maintenance during long-term treatment, as well. These results allow one to hypothesize that the loss of nitrate efficacy on venous pooling capability, but not on arterial tone, might constitute the more frequent cause of tolerance.

Administration, Cutaneous↗

PubMed1992

Diltiazem as adjunctive oral therapy in patients with chronic atrial fibrillation.

Digoxin frequently fails to control the heart rate in patients of chronic atrial fibrillation particularly during exertion. We have studied in 20 such patients the effect of adding diltiazem (180 mg/day) on resting and peak exercise heart rates. An attempt was also made to determine its effects on exercise tolerance by using treadmill and 6 minute walk test. Addition of diltiazem resulted in significant attenuation of heart rate both at rest and at peak exercise. The resting and exercise mean heart rates on digoxin alone were 98.9 +/- 21.5 b.p.m. and 160.2 +/- 35.68 b.p.m. respectively. After diltiazem this reduced to 78.7 +/- 12.30 b.p.m. at rest and 132.4 +/- 40.4 b.p.m. at peak exercise (p < 0.01). There was no significant effect on exercise tolerance. In conclusion, the addition of diltiazem substantially reduced the excessive heart rate response to exercise in digitalised patients of chronic atrial fibrillation.

Administration, Oral↗

PubMed1997

[Measuring stress hemodynamics in pulmonary circulation during the inpatient phase after myocardial infarct: a rightfully "forgotten" evaluation?].

UNLABELLED: In 123 consecutive patients pulmonary hemodynamics at rest and during exercise were measured 7-10 days after acute myocardial infarction and systemic thrombolysis. Right- and left-heart catheterizations were performed at the same session and repeated after 6 months. We investigated if right-heart catheterization could predict the number of stenotic or occluded coronaries, the angiographic ventricular function and/or, most important, if the patient would profit from revascularization by PTCA or coronary surgery. RESULTS: 1) Pulmonary hemodynamics at rest and during exercise did not correlate to the number of stenotic or occluded coronaries, but exercise tolerance did. 2) Correlation between ventricular function and pulmonary hemodynamics was weak. 3) Only patients with pathologically elevated pulmonary pressures at exercise showed profit from revascularization (increase of ejection fraction > 5% at control). This profit was closely correlated to the angiographic extent of ventricular damage. Consequences from our results: Individual exercise tolerance can easily be measured non-invasively. Ventricular function can be measured non-invasively as well by echocardiography. Measurement of pulmonary hemodynamics at rest and during exercise does not contribute to planning the future management of the postinfarction patient and does not replace coronarography when indicated by clinical or non-invasive parameters.

Adult↗

PubMed1984

[Role of hyperlipidemia in disorders of myocardial function in men with or without angina pectoris and post-infarction cardiosclerosis].

The paper is concerned with evaluation of myocardial function in men under 50 without the clinical manifestations of coronary heart disease (CHD), in patients with angina pectoris and postinfarction cardiosclerosis. The examinees were divided into groups with and without hyperlipidemia (HLP). The cholesterol level not less than 300 mg/100 ml (7.76 mmol/l) and the triglyceride level not less than 200 mg/100 ml (2.25 mmol/l) was regarded as hyperlipidemic. To judge myocardial function, use was made of the criterion of exercise tolerance on a treadmill and of polycardiography (PCG) and apical cardiography (ACG). It was established that in groups with HLP, the exercise tolerance was lower than in analogous clinical groups without HLP. PCG and ACG were also helpful in a more frequent detection of cardiodynamic disorders in HLP groups. The exercise test has shown that in HLP, the ischemic responses in CHD patients occur more readily and more frequently. Possible mechanisms of an adverse effect of HLP are discussed.

Adult↗

PubMed1999

Demasking of subclinical left ventricular dysfunction in anemic children.

OBJECTIVE: To study subclinical left ventricular dysfunction in anemic children. SETTING: Hospital. SUBJECTS: The study population consisted of 52 cases of anemia (16 mild, 14 moderate, 22 severe) and 20 normal age and height matched children aged between 7-12 years. METHODS: These children were subjected to Echocardiography on Ascuson XP model using 3.5 MHz Transducer during rest and immediately after maximum tolerated exercise on Quniton Model Q-5000 treadmill using modified Naughton protocol. Left ventricular end diastolic dimensions, left ventricular systolic dimension, fractional shortening, left ventricular end diastolic volume, systolic volume, stroke volume and ejection fraction were studied on M-mode echocardiography, and E/A ratio on doppler mode. RESULTS: Significant differences were observed in resting heart rate, gain in heart rate at peak exercise compared to basal values and double product, total exercise duration and metabolic equivalents at peak exercise in controls and anemic subjects. Left ventricular dysfunction was present in all severely anemic subjects after maximum tolerated exercise on treadmill. The only evidence of left ventricular diastolic dysfunction was in form of decreased left ventricular end diastolic volume after exercise in moderate and severely anemic subjects. CONCLUSIONS: Exercise is helpful in demasking subtle left ventricular dysfunctions in anemic subjects that are not detected during rest.

Anemia↗

PubMed1976

Angina in hypertensive patients. With particular reference to the negative chronotropic effects of sympatholytic therapy.

There was no significant difference in the blood pressure and heart rate response of hypertensive patients with and without angina to standardised exercise on a treadmill before and after anti-hypertensive treatment. There was no improvement in exercise tolerance in the hypertensive patients with angina treated with bethanidine, debrisoquine or guanethidine despite a reduction of resting and exercise heart rates after treatment. The negative chronotropic effect of these sympatholytic drugs was less than that of oxprenolol or propranolol, but the hypotensive response was greater. Both of these beta-receptor blocking drug produced an an improvement in exercise tolerance in patients with angina either alone or in combination with other hypotensive therapy. The best control of blood pressure and angina was often achieved by a combination of a sympatholytic drug and beta-receptor blocking drug. In hypertensive patients treated for several years, angina at presentation was occassionally reduced by reduction of blood pressure. Later onset of angina appeared to be unrelated to control of hypertension but to be due to coincidental coronary occlusion. There was no evidence that myocardial infarction was precipitated by postural or exercise hypotension although these effects occasionally precipitated angina.

Adrenergic beta-Antagonists↗

PubMed1999

The effect of fluvastatin on cardiac events in patients with symptomatic coronary artery disease during one year of treatment.

The primary objective of the present study was to investigate the cholesterol-lowering effect of fluvastatin on the incidence of cardiac events in hyperlipidaemic patients with symptomatic, clinically-diagnosed (exercise-ECG) coronary heart disease (CHD) during 1 year of treatment. Exercise tolerance, incidence of angina pectoris episodes, use of anti-anginal medication and intimal-medial-thickness (IMT subgroup) of the A. carotis were secondary endpoints. In the double-blind trial a total of 365 male and female patients with stable symptomatic CHD and a low-density lipoprotein cholesterol (LDL-C) above 160 mg/dl on a lipid-lowering diet were randomised to fluvastatin 40 mg (o.a.d. or b.i.d.) or placebo for 1 year. Fluvastatin lowered total cholesterol by 17% and LDL-C by 27%. There was a significantly lower incidence of cardiac events (cardiac death, nonfatal myocardial infarction, unstable angina pectoris) in the fluvastatin group (3 events) as compared to the placebo group (10 events) (P < 0.05). Exercise tolerance improved and the incidence of angina pectoris episodes decreased in both groups, but more pronounced on fluvastatin (n.s.). Exercise-ECG discontinuation due to angina pectoris and ST-segment depression decreased in the fluvastatin group by 55.6 and 70.9%, respectively, and in the placebo group by 39.6 and 46.5% (n.s.). At baseline, a subgroup of 76 patients showed a mean IMT value of 0.73 mm which remained uninfluenced in the fluvastatin and the placebo groups. Fluvastatin was safe and well tolerated. In conclusion, patients with symptomatic CHD get cardiovascular benefit from lipid-lowering therapy with fluvastatin even during the first year of treatment.

Adult↗

PubMed1986

[Effectiveness of the physical training of post-myocardial infarction patients with differing exertion tolerances].

A total of 159 men after myocardial infarction were examined. Of them 73 were engaged in physical training for 11 mos. Its efficacy was analysed after the results of bicycle ergometry taking account of initial exercise tolerance. A positive effect of physical training was noted both in the patients with high and low exercise tolerance. Raised physical working capacity was observed in parallel with the improved indices of the left ventricular contractility in accordance with the results of two-dimensional echocardiography. The authors also observed a favorable effect of physical training on lipoprotein metabolism, in particular a decrease in the value of the apo B/apo AI ratio was noted that might suggest a decrease in the inflow of cholesterol to the vascular wall and an enhanced outflow from it.

Adult↗

PubMed1992

Single lung transplantation in rats with fatal pulmonary hypertension.

Effects of single lung transplantation on fatal pulmonary hypertension were evaluated in rats receiving a lethal dose of monocrotaline. Inbred rats treated with monocrotaline (80 mg/kg) received a left lung isograft at 4 weeks (n = 9) and at 6 weeks (n = 6), when moderate and severe pulmonary hypertension, respectively, had developed. Medicated (n = 12) and nonmedicated rats (n = 12) served as control animals. Each rat was tested weekly with treadmill for exercise tolerance and oxygen consumption during a 10-week period after medication and after they were killed. Medicated control rats lost exercise tolerance and highest oxygen consumption per unit time consistently to the range of resting value (or 45% of nonmedicated control rats), and all died from severe pulmonary vascular occlusive disease with right ventricular hypertrophy before 10 weeks (right ventricular/left ventricular weight ratio of 1.16). All rats receiving a left lung isograft at 4 weeks survived and regained highest oxygen consumption per unit time (87% of nonmedicated control rats), with the lung transplant receiving 65% (nonmedicated control rats, 39%) of cardiac output and milder right ventricular hypertrophy (right ventricular/left ventricular weight ratio of 0.46). Except for one, all rats that received a left lung isograft at 6 weeks tolerated single lung transplantation, but they died soon after reperfusion because of pulmonary edema in the graft that received 58% of cardiac output with right ventricular/left ventricular weight ratio of 0.79. Results of single lung transplantation in rats were dependent on severity of pulmonary hypertension. In rats with moderate pulmonary hypertension, single lung transplantation was successful in reversing exercise intolerance and right ventricular hypertrophy. Single lung transplantation was unsuccessful when pulmonary hypertension was severe in the rat model because increased flow toward the lung transplant resulted in graft pulmonary edema.

Animals↗

PubMed1985

Rate-responsive ventricular pacing: clinical experience with the RS4-SRT pacing system.

Eighteen patients (11 men and 7 women) with symptomatic second or third degree atrioventricular block underwent implantation of the rate-responsive RS4-SRT pacing system. Exercise tolerance in RS4 mode was compared to that in VVI mode by randomized double-blind treadmill stress testing. Following hospital discharge, RS4 function was assessed by repeat exercise testing and 24-hour Holter monitoring. Difficulty in obtaining satisfactory P-wave amplitudes at implantation (mean 3.1 +/- 1.5 mV) resulted in prolonged implantation times (mean 79.4 +/- 26.4 minutes). Following implantation, 10 patients (58%) showed a significant ventricular rate response to exercise, seven did not, and one remained in sinus rhythm. For responders, peak ventricular paced rate and double product were significantly greater in RS4 than in VVI mode, being 101.8 +/- 5.8 vs. 74.3 +/- 0.4 beats per minute and 20.1 +/- 2.9 vs. 15.5 +/- 3.7 beats per minute X mmHg X 10(-3), respectively (p less than 0.001). However, treadmill times (10.5 +/- 2.6 vs. 9.7 +/- 3.3 minutes) and work done (5.51 +/- 2.01 vs. 4.97 +/- 2.33 joules X 10(-5] were not significantly different (p = 0.22). Following hospital discharge, repeat exercise testing and 24-hour Holter monitoring demonstrated RS4 function in 11 of 16 and 15 of 18 patients, respectively. We conclude that, due to unreliable atrial sensing, the RS4-SRT pacing system does not provide the reliable rate-responsiveness required to improve exercise tolerance.

Aged↗