Mechanism of exercise hypotension in patients with ischemic heart disease. Role of neurocardiogenically mediated vasodilation

Cardiovascular responses during resistance exercise after an aerobic session

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Diastolic and mean BP were higher during resistance exercise after aerobic exercise.

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Peak heart rate values were higher during resistance exercise after aerobic exercise.

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Aerobic exercise before resistance exercise promoted higher cardiovascular work.

Objective

To analyze the influence of previous aerobic exercise on cardiovascular responses during resistance exercise.

Methods

This is a crossover observational study. The sample included 19 normotensive men aged between 19 and 39 years. Subjects performed two experimental sessions in random order: resistance exercise (R: three sets of knee extension exercises with 40% of one repetition maximum) and aerobic exercise + resistance exercise (A + R: 30 min of aerobic exercise followed by R protocol). In both sessions, blood pressure (BP) and heart rate were monitored beat-by-beat by finger photoplethysmography.

Results

After aerobic exercise in the A + R session, there was a maintenance of systolic BP −2 (95% CI: −6; 2) mmHg (P = 0.35), diastolic 1 (95% CI: −2; 5) mmHg (P = 0.40) and mean BP 0 (95% CI: −4; 4) mmHg (P = 0.91) and an increase in heart rate 11 (95% CI: 7; 16) bpm (P < 0.001). Diastolic and mean BP increased and peak heart rate was higher during resistance exercise in the A + R session compared to the R session. Differences between sessions: diastolic BP 7 (95% CI: 2; 12) mmHg (P = 0.03); mean BP 8 (95% CI: 2; 13) mmHg (P = 0.05); and peak heart rate 18 (95% CI: 13; 23) bpm (P < 0.001). The increases in systolic BP during resistance exercise were similar between sessions 16 (95% CI: 6; 26) mmHg (P = 0.43).

Conclusion

Aerobic exercise before resistance exercise increased diastolic and mean BP and heart rate. However, due to the sample size of 19 individuals, the results must be interpreted with caution.

Relation of Risk of Atrial Fibrillation With Systolic Blood Pressure Response During Exercise Stress Testing (from the Henry Ford ExercIse Testing Project)

Decreases in systolic blood pressure during exercise may predispose to arrhythmias such as atrial fibrillation (AF) because of underlying abnormal autonomic tone. We examined the association between systolic blood pressure response and incident AF in 57,442 (mean age 54 ± 13 years, 47% women, and 29% black) patients free of baseline AF who underwent exercise treadmill stress testing from the Henry Ford ExercIse Testing project. Exercise systolic blood pressure response was examined as a categorical variable across clinically relevant categories (>20 mm Hg: referent; 1 to 20 mm Hg, and ≤0 mm Hg) and per 1-SD decrease. Cox regression, adjusting for demographics, cardiovascular risk factors, medications, history of coronary heart disease, history of heart failure, and metabolic equivalent of task achieved, was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between systolic blood pressure response and incident AF. Over a median follow-up of 5.0 years, a total of 3,381 cases (5.9%) of AF were identified. An increased risk of AF was observed with decreasing systolic blood pressure response (>20 mm Hg: HR 1.0, referent; 1 to 20 mm Hg: HR 1.09, 95% CI 0.99, 1.20; ≤0 mm Hg: HR 1.22, 95% CI 1.06 to 1.40). Similar results were obtained per 1-SD decrease in systolic blood pressure response (HR 1.08, 95% CI 1.04 to 1.12). The results were consistent when stratified by age, sex, race, hypertension, and coronary heart disease. In conclusion, our results suggest that a decreased systolic blood pressure response during exercise may identify subjects who are at risk for developing AF.

Receiver operating characteristic (ROC) curves and the definition of threshold levels to diagnose coronary artery disease on electrocardiographic stress testing. Part I: The use of ROC curves in diagnostic medicine and electrocardiographic markers of ischaemia

A common problem in diagnostic medicine, when performing a diagnostic test, is to obtain an accurate discrimination between 'normal' cases and cases with disease, owing to the overlapping distributions of these populations. In clinical practice, it is exceedingly rare that a chosen cut point will achieve perfect discrimination between normal cases and those with disease, and one has to select the best compromise between sensitivity and specificity by comparing the diagnostic performance of different tests or diagnostic criteria available. Receiver operating characteristic (or receiver operator characteristic, ROC) curves allow systematic and intuitively appealing descriptions of the diagnostic performance of a test and a comparison of the performance of different tests or diagnostic criteria. This review will analyse the basic principles underlying ROC curves and their specific application to the choice of optimal parameters on exercise electrocardiographic (ECG) stress testing. Part I will focus on theoretical description and analysis along with reviewing the common problems related to the diagnosis of myocardial ischaemia by means of exercise ECG stress testing. Part II will be devoted to applying ROC curves to available diagnostic criteria through the analysis of ECG stress test parameters.

Electrocardiographic exercise stress testing: an update beyond the ST segment

Routine exercise testing is frequently ordered to evaluate a patient's cardiovascular performance. The test is more direct and less expensive than imaging technology, and derives valuable information. New variables such as dyspnea and heart rate recovery, as well as integrated scores, provide incremental value to conventional analysis of exercise-induced angina or electrocardiographic changes. Considerations relating to test accuracy in women need to be weighed. This paper seeks to make physicians aware of the current status of the test, and improve their understanding of and ability to integrate new variables and scores to more effectively manage their patients.

Failure to raise blood pressure during exercise is a poor prognostic sign in patients with hypertrophic non-obstructive cardiomyopathy

Sudden cardiac death is a well-documented complication of hypertrophic cardiomyopathy and additionally, failure to raise blood pressure (BP) during exercise has been associated with a poor outcome. The present study group comprised 58 patients with hypertrophic non-obstructive cardiomyopathy (HNCM) who were receiving beta-blocker therapy. All patients underwent submaximal exercise radionuclide ventriculography (RNVG) to evaluate left ventricular (LV) function at both rest and peak exercise. Patients were divided into 2 groups based on the increase in systolic BP during exercise (ie, group A <30% or group N >/=30% of resting systolic BP) and were involved in long-term follow-up (10.4+/-4.0 years). Group A comprised 29% of the subjects. Age and workload at peak exercise were similar in the 2 groups. LV end-diastolic dimension was smaller and the interventricular septum was thicker in group A. LV ejection fraction on RNVG was similar in the 2 groups at rest and at peak exercise. During the follow-up period, more patients in group A than group N suffered syncopal attack (29% vs 5%, p<0.05) and cardiac sudden death (24% vs 2%, p<0.05). Patients with HNCM whose BP fails to rise during exercise have a poor prognosis.

Forearm vasoconstriction during dynamic leg exercise in patients with chronic heart failure

Previous studies assessing vascular responses in nonexercising beds during exercise in patients with chronic heart failure (CHF) have yielded varying results. We proposed that the clinical and hemodynamic severity of heart failure may explain some of the variation. We reasoned that diastolic ventricular interaction (DVI), by limiting the ability of such patients to increase left ventricular (LV) volume and stroke volume during exercise, would attenuate baroreflex activation, resulting in increased sympathetic activation and hence exaggerated vasoconstriction. We hypothesized therefore that vasoconstriction in nonexercising beds would be exaggerated in patients with symptomatic and hemodynamically severe heart failure, particularly if associated with DVI. We measured forearm vascular resistance (FVR) during semierect cycle exercise in 22 CHF patients and 23 control subjects. DVI was assessed by measuring changes in ventricular volumes (radionuclide ventriculography) during volume unloading (-30 mm Hg lower-body negative pressure) in the heart failure patients and was inferred when LV end-diastolic volume paradoxically increased. Patients with symptoms of heart failure developed larger increases in FVR during exercise than did asymptomatic patients. There were significant correlations between the change in FVR during peak exercise and the resting mean pulmonary arterial pressure and pulmonary vascular resistance. CHF patients with DVI developed exaggerated increases in FVR (median [25th to 75th percentile]) compared with the remaining patients during low-workload exercise (138 [66 to 171] vs 6.4 [-4.3 to 28] units, P = 0.002) and during peak exercise (160 [90 to 384] vs 61 [-7.4 to 75] units, P < 0.02). Vasoconstriction in nonexercising beds is exaggerated in CHF patients with clinically and hemodynamically severe heart failure, particularly if associated with DVI. This may explain some of the reported variation in the degree of sympathetic activation that occurs during exercise in CHF patients.

Forearm vascular responses during semierect dynamic leg exercise in patients following myocardial infarction

We assessed forearm vascular and blood pressure responses to dynamic leg exercise in patients 7 and 28 days postmyocardial infarction. To determine a possible association between abnormal exercise vascular responses and baroreflex dysfunction, integrated and carotid baroreflex sensitivity and forearm vascular responses (during application of subhypotensive lower body negative pressure) were assessed. On day 7, 42 patients were compared with 21 age- and sex-matched controls. All subjects were assessed for (1) forearm vascular resistance during semierect exercise, (2) blood pressure measurements during erect treadmill exercise, and (3) integrated, cardiopulmonary, and carotid baroreceptor sensitivity. These studies were repeated in 13 patients on day 28. Forearm vascular resistance increased during exercise by 36% +/- 63% in patients versus 121% +/- 105% in controls (P = 0.0001), and fell in 15 patients, a response seen in none of the controls. Exercise hypotension was demonstrated in 5 patients, all of whom had abnormal vasodilator vascular responses. Those patients with vasodilator responses had a lower left ventricular ejection fraction (52% +/- 12% vs 62% +/- 9%; P = 0.007), and lower cardiopulmonary mechanoreceptor sensitivity (-6.6 +/- 3.9 units vs +6.4 +/- 10.4 units, P = 0.02) than those with constrictor responses, respectively. In the 13 patients studied on day 28, the change in forearm vascular resistance was similar to that observed on day 7 (36% +/- 63% vs 46% +/- 73%). Paradoxical vasodilation of forearm vessels during leg exercise is common in patients studied 7 and 28 days postmyocardial infarction, and is associated with lower left ventricular ejection fraction and abnormal vascular responses during subhypotensive lower body negative pressure.

Exercise-induced abnormal blood pressure responses are related to subendocardial ischemia in hypertrophic cardiomyopathy

OBJECTIVES

We examined by thallium-201 scintigraphy whether exercise-induced abnormal blood pressure response (BPR) is related to myocardial ischemia.

BACKGROUND

Hemodynamic instabilities during exercise in patients with hypertrophic cardiomyopathy (HCM) are considered to be caused by abnormal reflex control of vascular resistance.

METHODS

In 105 patients with HCM, exercise thallium scintigraphy was performed by means of a multistage, symptom-limited bicycle ergometer exercise test.

RESULTS

Eighty-eight patients had normal BPR (> or = 25 mm Hg from baseline to peak exercise), and 17 had abnormal BPR (<25 mm Hg). Clinical characteristics including age, the prevalence of obstruction, New York Heart Association functional class and echocardiographic measurements were similar between the two groups. Left ventricular end-diastolic pressure was significantly higher in patients with abnormal BPR than in those with normal BPR (18+/-8 vs. 14+/-5 mm Hg, p < 0.05). Exercise-induced perfusion abnormalities including fixed and reversible perfusion defects, and left ventricular cavity dilatation (LVCD) were identified in 72 (69%) of 105 study patients. Left ventricular cavity dilatation indicates subendocardial hypoperfusion and is a marker of diffuse subendocardial ischemia. The prevalence of fixed or reversible perfusion defects was similar between the two groups. Patients with abnormal BPR had the higher prevalence of LVCD as compared to those with normal BPR (47.1 vs. 10%, p < 0.0002). Multiple logistic regression analysis revealed that LVCD was independently associated with abnormal BPR (odds ratio 3.76, 95% confidence interval 1.61 to 8.76).

CONCLUSIONS

Exercise-induced abnormal BPRs in patients with HCM are related to subendocardial ischemia during exercise.

Do you mind standing?: cognitive changes in orthostasis

This initial study examines cognitive function in individuals with asymptomatic orthostatic hypotension. Cerebral hypoperfusion accompanying repeated episodes of orthostatic hypotension may eventually produce some cerebral structural deterioration which, depending on foci, could compromise cognitive function. Subjects (aged 55 to 74 years) were relatively healthy women and men, the majority of whom were being treated for non-insulin-dependent diabetes mellitus. Blood pressure (BP) and pulse were measured under supine and upright posture. The difference between BP and pulse under supine and standing conditions indexed orthostatic hypotension. About 1 hr after evaluation of orthostatic hypotension, cognitive testing was performed with individuals comfortably seated. Results showed that, irrespective of possible confounders, including depression, decreased systolic BP in response to upright posture predicted slower reaction times and compromised serial list learning, although sparing immediate and working memory. Orthostatic hypotension, measurable in more than 4% of the elderly, is a hitherto unexplored source of cognitive decline.

Peak exercise blood pressure stratified by age and gender in apparently healthy subjects

OBJECTIVE

To determine the peak blood pressure responses during symptom-limited exercise in a large sample of apparently healthy subjects, including both men and women over a wide range of ages.

DESIGN

We retrospectively studied the blood pressure response during maximal treadmill exercise testing with use of the Bruce protocol in apparently healthy subjects.

MATERIAL AND METHODS

Peak exercise blood pressures in 7,863 male and 2,406 female apparently healthy subjects who underwent a screening treadmill exercise test with the Bruce protocol between 1988 and 1992 were analyzed by age and gender.

RESULTS

In this large referral population of apparently healthy subjects, peak exercise systolic and diastolic blood pressures and delta systolic blood pressure (rest to peak exercise) were higher in men than in women and were positively associated with age. In men, the 90th percentile of systolic blood pressure increased from 210 mm Hg for the age decade 20 to 29 years to 234 mm Hg for ages 70 to 79 years; the corresponding increase among women was from 180 mm Hg to 220 mm Hg. Delta diastolic blood pressure also increased with advancing age. The difference in peak and delta systolic blood pressures between men and women seemed to decrease after age 40 to 49 years. Exercise hypotension, defined as peak exercise systolic pressure less than rest systolic pressure, occurred in 0.23% of men and 1.45% of women and was not significantly related to age.

CONCLUSION

Overall, peak exercise systolic and diastolic, as well as delta systolic, blood pressures were higher in men than in women and increased with advancing age. The reported data will enable clinicians to interpret more accurately the significance of peak exercise blood pressure response in a subject of a specific age and gender and will allow investigators to define exercise hypertension in statistical terms stratified by age and gender.