Increased diastolic blood pressure response to exercise testing when coronary artery disease is suspected. An indication of severity

A mathematical modelling analysis of the response of blood pressure and heart rate to submaximal exercise

Objective: According to Golden ratio (GR) and Fibonacci sequence, models of the organisation of various structures can be encountered in biology, medicine, architecture and engineering. Recent studies indicate that GR can be highlighted in the organisation and physiological functioning of the cardiovascular system. The aim of this study was to investigate the cardiovascular homeostasis during rest and exercise testing by determining the GR validity at the dynamic level of systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) values. Methods and Results: We used data obtained from a cardiovascular testing of a group of 236 young healthy subjects (mean age of 19.35 ± 1.92 years). We realised a double assessment of subjects (HR and BP), at rest and immediately after a six minutes submaximal exercise test (Astrand and Rhyming protocol). The investigated group showed a normal cardiovascular reactivity in subjects. GR harmonic rhythm can be identified in the correlation of hemodynamic parameters of HR and SBP, respectively of SBP and DBP, at rest. The differences between means of the ratios (SBP/HR and SBP/DBP), at rest and after effort, were statistically significant (p < .001), with a large effect size. Conclusions: We confirm that the rest state determines the harmonisation of SBP and HR, respectively, of SBP and DBP values, both ratios being very close to GR value. From the perspective of these cardiovascular parameters, the human body is designed to function in the harmonic regime at rest and to temporarily get out of synchronisation during exercise.

Exercise Blood Pressure Guidelines: Time to Re-evaluate What is Normal and Exaggerated?

Blood pressure responses to graded exercise testing can provide important diagnostic and prognostic information. While published guidelines outline what constitutes a "normal" and "abnormal" (i.e., exaggerated) blood pressure response to exercise testing, the widespread use of exaggerated blood pressure responses as a clinical tool is limited due to sparse and inconsistent data. A review of the original sources from these guidelines reveals an overall lack of empirical evidence to support both the normal blood pressure responses and their upper limits. In this current opinion, we critically evaluate the current exercise blood pressure guidelines including (1) the normal blood pressure responses to graded exercise testing; (2) the upper limits of this normal response; (3) the blood pressure criteria for test termination; and (4) the thresholds for exaggerated blood pressure responses. We provide evidence that exercise blood pressure responses vary according to subject characteristics, and subsequently a re-evaluation of what constitutes normal and abnormal responses is necessary to strengthen the clinical utility of this assessment.

Differential Post-Exercise Blood Pressure Responses between Blacks and Caucasians

Post-exercise hypotension (PEH) is widely observed in Caucasians (CA) and is associated with histamine receptors 1- and 2- (H1R and H2R) mediated post-exercise vasodilation. However, it appears that blacks (BL) may not exhibit PEH following aerobic exercise. Hence, this study sought to determine the extent to which BL develop PEH, and the contribution of histamine receptors to PEH (or lack thereof) in this population. Forty-nine (22 BL, 27 CA) young and healthy subjects completed the study. Subjects were randomly assigned to take either a combined H1R and H2R antagonist (fexofenadine and ranitidine) or a control placebo. Supine blood pressure (BP), cardiac output and peripheral vascular resistance measurements were obtained at baseline, as well as at 30 min, 60 min and 90 min after 45 min of treadmill exercise at 70% heart rate reserve. Exercise increased diastolic BP in young BL but not in CA. Post-exercise diastolic BP was also elevated in BL after exercise with histamine receptor blockade. Moreover, H1R and H2R blockade elicited differential responses in stroke volume between BL and CA at rest, and the difference remained following exercise. Our findings show differential BP responses following exercise in BL and CA, and a potential role of histamine receptors in mediating basal and post-exercise stroke volume in BL. The heightened BP and vascular responses to exercise stimulus is consistent with the greater CVD risk in BL.

Flow-mediated dilation and exercise blood pressure in healthy adolescents

OBJECTIVES

Exercise blood pressure is a robust predictor of cardiovascular disease risk. Endothelial dysfunction occurs early in development of cardiovascular disease and is associated with greater exercise blood pressure in adults. However, it is not yet clear whether endothelial function is associated with exercise blood pressure in youth. The purpose of this study was to examine the relationship between endothelial function, indexed by brachial artery flow-mediated dilation, and submaximal exercise blood pressure in healthy adolescents.

DESIGN

Cross-sectional study.

METHODS

Adolescents (N=45) completed a graded submaximal treadmill test. Blood pressure was measured during rest and each exercise stage. Ultrasound measurement of brachial artery flow-mediated dilation was completed on a separate visit. Pearson correlations and multiple regression were used to assess the unadjusted and multivariate adjusted associations between flow-mediated dilation and exercise blood pressure, respectively.

RESULTS

Lower flow-mediated dilation was associated with lower diastolic blood pressure (r=0.37, p=0.01) and greater pulse pressure (r=-0.38, p=0.01) during exercise. The significance did not change when adjusting for age, gender, fitness, or resting blood pressure. Exploratory analyses suggest that flow-mediated dilation was associated with exercise diastolic blood pressure primarily among adolescents with low resting diastolic blood pressure.

CONCLUSIONS

Studies in youth are important to understand the early pathogenesis of cardiovascular disease. Findings from this study suggest that endothelial function may play a role in regulating blood pressure responses during submaximal exercise in healthy adolescents.

The effect of different doses of aerobic exercise training on exercise blood pressure in overweight and obese postmenopausal women

OBJECTIVE

Abnormally elevated exercise blood pressure is associated with an increased risk of cardiovascular disease. Aerobic exercise training has been shown to reduce exercise blood pressure. However, it is unknown whether these improvements occur in a dose-dependent manner. The purpose of the present study was to determine the effect of different doses of aerobic exercise training on exercise blood pressure in obese postmenopausal women.

METHODS

Participants (N = 404) were randomized to one of four groups--groups with 4, 8, or 12 kcal/kg of energy expenditure per week or a nonexercise control group--for 6 months. Exercise blood pressure was obtained during the 50-watt stage of a cycle ergometer maximal exercise test.

RESULTS

There was a significant reduction in systolic blood pressure at 50 watts in the 4 kcal/kg per week (-10.9 mm Hg, P < 0.001), 8 kcal/kg per week (-9.9 mm Hg, P = 0.022), and 12 kcal/kg per week (-13.7 mm Hg, P < 0.001) compared with control (-4.2 mm Hg). Only the highest exercise training dose significantly reduced diastolic blood pressure (-4.3 mm Hg, P = 0.033) compared with control. In addition, resting blood pressure was not altered after exercise training (P > 0.05) compared with control and was not associated with changes in exercise systolic (r = 0.09, P = 0.09) or diastolic (r = 0.10, P = 0.08) blood pressure.

CONCLUSIONS

Aerobic exercise training reduces exercise blood pressure and may be more modifiable than changes in resting blood pressure. A high dose of aerobic exercise is recommended to successfully reduce both exercise systolic and diastolic blood pressure and therefore may attenuate the cardiovascular disease risk associated with abnormally elevated exercise blood pressure.

Increased response of diastolic blood pressure to exercise in patients with coronary artery disease: an index of latent ventricular dysfunction?

OBJECTIVE

To determine whether an abnormal response of diastolic blood pressure during treadmill exercise stress testing correlated with the number of obstructed vessels and with left ventricular systolic function in patients with coronary artery disease.

DESIGN

Diastolic blood pressure was measured invasively during exercise stress testing and coronary angiograms and left ventriculograms were obtained at rest in patients with coronary artery disease. The abnormal (> or = 15 mm Hg) diastolic blood pressure response was compared with the number of obstructed coronary arteries and with left ventricular systolic function.

SETTING

Two tertiary referral centres.

PATIENTS

50 consecutive patients (mean age 57 years) with coronary artery disease.

MAIN OUTCOME MEASURES

The increase in diastolic blood pressure during exercise and its correlation with the appearance and disappearance of ST segment deviation, resting left ventricular systolic function, and the number of obstructed coronary arteries.

RESULTS

Group 1: 10 (20%) patients (three with one, four with two, and three with three vessel coronary artery disease) (mean (SD) age 54.7 (12) years) had an abnormal diastolic blood pressure response that appeared 1.2 (0.3) min before ST segment deviation and became normal 0.9 (0.3) min after the ST segment returned to normal. Group 2: 40 (80%) patients (12 with one, 16 with two, and 12 with three vessel coronary arteries disease) (aged 56.8 (8.2) years) had a normal diastolic blood pressure response to stress testing. The ejection fraction (46.3 (5)%) and cardiac index (2.6 (0.1) 1/min/m2) in group 1 were less than in group 2 (61.6 (4.2)% and 3.8 (0.3) 1/min/m2 respectively, p < or = 0.001). The end systolic volume was greater in group 1 than in group 2: 38.7 (0.7 ml/m2 v 28.2 (2.1) ml/m2, p < or = 0.001.

CONCLUSION

In patients with coronary artery disease an abnormal increase in diastolic blood pressure during exercise stress testing correlated well with left ventricular systolic function at rest but not with the number of obstructed coronary arteries. The abnormal response of diastolic blood pressure probably reflects deterioration of myocardial function.

Raised exercise diastolic blood pressure as indicator of ischaemic left ventricular dysfunction

91 (16.8%) of 541 consecutive patients investigated for chest pain or after recent uncomplicated myocardial infarction had a rise in diastolic blood pressure (DBP) of more than 15 mm Hg during a symptom-limited treadmill test. 63 also had electrocardiographic evidence of ischaemia, but 28 did not have 1 mm ST segment depression, of whom 24 had angiographic evidence of more than 70% stenosis of two or more major coronary arteries. 55 of these 91 patients underwent coronary artery bypass surgery; repeat angiography in 22 at 12 months showed an improved left ventricular ejection fraction in 18 who had a normal postoperative DBP response, but no change in ejection fraction in the 4 who still had an abnormal rise in DBP on exercise. Exercise-induced ischaemia may cause a reversible fall in cardiac output that sometimes leads to reflex vasoconstriction and a rise in DBP before a fall in systolic blood pressure or ECG evidence of ST segment depression. An abnormal DBP response to exercise may identify some patients at high risk of myocardial infarction who might otherwise have false-negative exercise tests.

Prediction of left ventricular function during supine bicycle ergometer exercise in angina-free patients with old myocardial infarction

We investigated whether or not left ventricular function during dynamic exercise in angina-free patients with old myocardial infarction could be estimated using resting left ventricular function and noninvasive parameters determined during exercise. We studied 70 patients with old myocardial infarction by measuring hemodynamic parameters during supine multistage bicycle ergometer exercise. Coronary arteriography and left ventriculography were performed: then the left ventricular ejection fraction and left ventricular end-diastolic volume were measured. The parametric changes (delta) between rest and peak exercise were determined. Significant positive correlations were observed between cardiac index (CI) at rest and at peak exercise (r = 0.62, p less than 0.001), as well as between pulmonary artery wedge pressure (PAWP) at rest and at peak exercise (r = 0.72, p less than 0.001). Multiple regression analysis indicated that CI and PAWP at peak exercise as dependent variables were best described by the equations: CI at peak exercise = 1.074 [CIrest] +0.031 [delta HR] + 0.004 [ExD] + 0.018 [LVEF] - 1.560 (r = 0.79, p less than 0.001), PAWP at peak exercise = 0.994 [PAWPrest] - 0.181 [LVEF] + 0.203 [delta DBP] -0.076 [delta HR] -21.488 (r = 0.80, p less than 0.001). These data suggested that CI and PAWP during dynamic exercise in angina-free patients with old myocardial infarction could be predicted using noninvasive parameters, such as increments of blood pressure and heart rate as well as exercise duration, together with data on resting left ventricular function, such as resting CI, resting PAWP, and resting left ventricular ejection fraction (LVEF).

Exercise-induced ST segment depression in the diagnosis of multivessel coronary disease: a meta analysis

To evaluate the variability in the reported accuracy of the exercise electrocardiogram (ECG) for predicting severe coronary disease, meta analysis was applied to 60 consecutively published reports comparing exercise-induced ST depression with coronary angiographic findings. The 60 reports included 62 distinct study groups comprising 12,030 patients who underwent both tests. Both technical and methodologic factors were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity 81% [range 40% to 100%, SD 12%]; mean specificity 66% [range 17% to 100%, SD 16%]). All three variables found to be significantly and independently related to sensitivity were methodologic (the exclusion of patients with right bundle branch block, the comparison with another exercise test thought to be superior in accuracy and the exclusion of patients taking digitalis). Exclusion of patients with right bundle branch block and comparison with a "better" exercise test were both significantly associated with sensitivity for the prediction of triple vessel or left main coronary artery disease. Adjustment of exercise-induced ECG changes for changes in heart rate was strongly associated with the specificity for critical disease (partial R2 = 0.436, p = 0.0001).

Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.