Exercise Test Interpretation

Effects of respiratory muscle work on blood flow distribution during exercise in heart failure

Heart failure (HF) patients have a reduced cardiac reserve and increased work of breathing. Increased locomotor muscle blood flow demand may result in competition between respiratory and locomotor vascular beds. We hypothesized that HF patients would demonstrate improved locomotor blood flow with respiratory muscle unloading during activity. Ten patients (ejection fraction = 31 +/- 3%) and 10 controls (CTL) underwent two cycling sessions (60% peak work). Session 1 (S1): 5 min of normal breathing (NB), 5 min respiratory muscle unloading with a ventilator, and 5 min of NB. Session 2 (S2): 5 min NB, 5 min of respiratory muscle loading with inspiratory resistance, and 5 min of NB. Measurements included: leg blood flow (LBF, thermodilution), cardiac output (Q), and oesophageal pressure (P(pl), index of pleural pressure). S1: P(pl) was reduced in both groups (HF: 73 +/- 8%; CTL: 60 +/- 13%, P < 0.01). HF: Q increased (9.6 +/- 0.4 vs. 11.3 +/- 0.8 l min(-1), P < 0.05) and LBF increased (4.8 +/- 0.8 vs. 7.3 +/- 1.1 l min(-1), P < 0.01); CTL: no changes in Q (14.7 +/- 1.0 vs. 14.8 +/- 1.6 l min(-1)) or LBF (10.9 +/- 1.8 vs. 10.3 +/- 1.7 l min(-1)). S2: P(pl) increased in both groups (HF: 172 +/- 16%, CTL: 220 +/- 40%, P < 0.01). HF: no change was observed in Q(10.0 +/- 0.4 vs. 10.3 +/- 0.8 l min(-1)) or LBF (5.0 +/- 0.6 vs. 4.7 +/- 0.5 l min(-1)); CTL: increased (15.4 +/- 1.4 vs. 16.9 +/- 1.5 l min(-1), P < 0.01) and LBF remained unchanged (10.7 +/- 1.5 vs. 10.3 +/- 1.8 l min(-1)). These data suggest HF patients preferentially steal blood flow from locomotor muscles to accommodate the work of breathing during activity. Further, HF patients are unable to vasoconstrict locomotor vascular beds beyond NB when presented with a respiratory load.

High blood pressure response to stress ergometry could predict future hypertension

BACKGROUND

Previous studies have shown that exaggerated blood pressure (BP) during exercise is a valid risk predictor for future hypertension in most men and women, yet the use of ergometry as a means of early detection of incipient hypertension still requires confirmation.

OBJECTIVES

To assess the clinical utility of exercise BP measurement for the evaluation of risk for developing new-onset hypertension.

METHODS

Thirty individuals with normal BP were enrolled in this study and were subsequently divided into two groups: 13 persons with in-exercise hypertension were compared with 17 matched persons who were normotensive during ergometry. Their blood pressure was monitored during follow-up of two years.

RESULTS

More individuals in the exercise-hypertensive group developed hypertension after one or two years than those normotensive during the exercise (respectively, one year: 3 vs.0, p=0.03, two years: 10 vs. 1, p<0.0001). Both the systolic and diastolic BPs significantly differed between the two groups. Eighty four percent of those with exaggerated BP (>or=210 mm Hg) during the treadmill exercise developed hypertension after 2 years. The sensitivity and specificity of in-exercise hypertension for predicting its 2 year occurrence were, respectively, 91% and 84%.

CONCLUSION

Even in the absence of hypertension, its development during stress ergometry could be considered a predictive marker for the future development of hypertension, and can be a potential tool for identifying normotensive individuals at high risk. These individuals should be followed up and their BP controlled for a long time.

Usefulness of an exaggerated systolic blood pressure response to exercise in predicting myocardial perfusion defects in known or suspected coronary artery disease

The clinical importance of an exaggerated systolic blood pressure (BP) response to exercise, or exercise hypertension, is unclear. We have previously reported that exercise hypertension is associated with less severe angiographic coronary artery disease. This study sought to examine the association between exercise hypertension and ischemic "burden," as assessed by thallium-201 single-photon emission computed tomography. The cohort was comprised of consecutive adults (2,216 men, 1,229 women) referred for symptom-limited exercise thallium testing to evaluate known or suspected coronary artery disease. The main variable measured was exercise hypertension, defined as a peak systolic BP > or =210 mm Hg in men and > or =190 mm Hg in women. Thallium perfusion defects were described as: (1) any perfusion abnormality, (2) reversible abnormalities, and (3) any abnormality in > or =3 of 12 myocardial segments ("extensive abnormalities"). Exercise hypertension was present in 1,319 subjects (39%). Patients with exercise hypertension were less likely to have any thallium perfusion abnormality (16% vs 25%, odds ratio [OR] 0.58, 95% confidence intervals [CI] 0.49 to 0.69, p <0.001), reversible thallium abnormalities (7% vs 12%, OR 0.71, 95% CI 0.57 to 0.90, p <0.001), and extensive abnormalities (8% vs 14%, OR 0.53, 95% CI 0.42 to 0.67, p <0.001). After adjusting for possible confounders, the same trend was seen. During 6 years of follow-up there were 283 deaths with no association between exercise hypertension and mortality risk. Thus, exercise hypertension is associated with a lower likelihood of myocardial perfusion abnormalities and is not associated with an increased mortality rate.

The appearance of gallop rhythm after exercise stress testing

BACKGROUND AND HYPOTHESIS

Although it is generally assumed that the appearance of an early diastolic gallop, or third heart sound, appearing immediately after exercise during treadmill stress testing, indicates the presence of serious myocardial disease, no systemically collected data are available to test this hypothesis.

METHODS

The author performed auscultation on 3,679 patients undergoing routine treadmill testing together with thallium-201 perfusion scans. Exercise-induced diastolic sounds were related to the available clinical information and electrocardiographic and nuclear test results. These findings were compared with those of 665 randomly selected patients undergoing stress testing in whom such sounds were absent.

RESULTS

A total of 165 patients had audible third heart sounds (Group 1). In comparison with those patients lacking such sounds (Group 2), there was a considerably greater prevalence of myocardial scarring (68.5 vs. 26.9%), abnormal lung uptake of thallium (40 vs. 12.8%), diabetes mellitus (20.6 vs. 6.2%), and left bundle-branch block on the resting electrocardiogram (ECG) (15.1 vs. 1.2%). In addition, 65 patients (39.3%) had dilatation of the left ventricle after exercise; 31 (18.8%) of these were also dilated at rest, but only 2 (1.2%) had a drop in blood pressure during stress. In those individuals also subjected to nuclear ventriculography, the average resting ejection fraction was 35%. Estimated exercise capacity was generally reduced in Group 1 (average peak of 6.6 METs), but 29 (17.6%) exceeded 9 METs. Sensitivity and specificity of electrocardiographic ST depression were relatively poor in the detection of perfusion defects within this group (36 and 62%, respectively). Of the 39 patients in Group 1 with a normal resting ECG, 19 (48.7%) had scar (usually posterior or lateral) on nuclear scans. In an additional 10 of this group, nuclear evidence of ischemia (often extensive) was found.

CONCLUSIONS

An early or mid-diastolic gallop sound developing after exercise virtually always signifies myocardial disease with reduced myocardial function. Common associated findings are prior infarction (with or without associated ischemia), diabetes, and left bundle-branch block. When found in the presence of a normal resting ECG, this sound commonly signals the presence an occult left ventricular scar and, less commonly, extensive myocardial ischemia. In those patients manifesting such sounds, electrocardiographic ST changes in response to exercise appear limited in the detection of coronary ischemia.

Effects of pregnancy on the electrocardiogram in healthy subjects during strenuous exercise

OBJECTIVE

Our purpose was to examine the nature and the frequency of electrocardiographic changes at rest and after bicycle exercise in early and late gestation compared with a group of nonpregnant subjects.

STUDY DESIGN

Thirty-nine pregnant subjects had electrically braked bicycle exercise early and late in gestation. Eight nonpregnant subjects served as controls. Twelve-lead electrocardiograms were obtained during rest, exercise, and recovery. All electrocardiograms were analyzed by a cardiologist blinded to subject group and stage of the pregnancy. Data were analyzed by analysis of variance for repeated measures, and contingency tables were used to compare findings at rest and during exercise between the time periods. A p value < 0.05 was considered significant.

RESULTS

T-wave inversion in V2 was more frequent in the pregnant than the nonpregnant subjects (p < 0.01). Subjects "late" in pregnancy had significantly fewer Q waves in II, III, and aVF than the nonpregnant group did. With exercise the time to onset of maximum ST depression was significantly shorter during pregnancy.

CONCLUSION

Although minor electrocardiographic charges were found at rest and during exercise between the two groups, these should be considered normal unless associated with significant symptoms.