The accuracy of the electrocardiogram during exercise stress test based on heart size.

BACKGROUND: Multiple studies have shown that the exercise electrocardiogram (ECG) is less accurate for predicting ischemia, especially in women, and there is additional evidence to suggest that heart size may affect its diagnostic accuracy. HYPOTHESIS: The purpose of this investigation was to assess the diagnostic accuracy of the exercise ECG based on heart size. METHODS: We evaluated 1,011 consecutive patients who were referred for an exercise nuclear stress test. Patients were divided into two groups: small heart size defined as left ventricular end diastolic volume (LVEDV) <65 mL (Group A) and normal heart size defined as LVEDV ≥65 mL (Group B) and associations between ECG outcome (false positive vs. no false positive) and heart size (small vs. normal) were analyzed using the Chi square test for independence, with a Yates continuity correction. LVEDV calculations were performed via a computer-processing algorithm. SPECT myocardial perfusion imaging was used as the gold standard for the presence of coronary artery disease (CAD). RESULTS: Small heart size was found in 142 patients, 123 female and 19 male patients. There was a significant association between ECG outcome and heart size (χ(2) = 4.7, p = 0.03), where smaller hearts were associated with a significantly greater number of false positives. CONCLUSIONS: This study suggests a possible explanation for the poor diagnostic accuracy of exercise stress testing, especially in women, as the overwhelming majority of patients with small heart size were women.

Exercise testing in the presence of complete heart block.

A 28-yr-old female presented for preoperative evaluation. The resting ECG revealed sinus arrhythmia with complete heart block with a junctional escape rhythm and a ventricular rate of 43 bpm. The patient was in no apparent distress, and resting blood pressure was 80/50 mm Hg. Physical examination was largely unremarkable, with the exception of a soft, nontender, movable abdominal mass. The patient complained of mild dyspnea with stair climbing, but she was otherwise asymptomatic. Although high-grade atrioventricular (AV) block is considered a relative contraindication for exercise testing, this patient was referred for an exercise ECG stress test to assist in determining whether a electronic pacemaker or other therapy was necessary. A symptom-limited maximal ECG treadmill test was performed using the Bruce protocol. The resting HR before the test was 47 bpm, and resting blood pressure was 70/50 mm Hg. Beginning with the first stage of the test, sinus rhythm with a first-degree AV block was observed. The patient achieved 10.2 METs, with an HRpeak of 122 bpm and a peak blood pressure of 122/70 mm Hg. No ectopy was noted during exercise, no ST segment changes occurred during exercise or recovery, and the patient remained asymptomatic. The test was terminated because of the patient's inability to keep pace with the treadmill. On the basis of these results, no medical therapy or electronic pacemaker was recommended at this time, and the patient was permitted to undergo surgery for uterine fibroid tumors. This case illustrates that although complete heart block is a relative contraindication to exercise testing in some patients, the benefits of testing outweigh the risks.

Caffeinated beverage intake and the risk of heart disease mortality in the elderly: a prospective analysis.

BACKGROUND: Motivated by the possibility that caffeine could ameliorate the effect of postprandial hypotension on a high risk of coronary events and mortality in aging, we hypothesized that caffeinated beverage consumption decreases the risk of cardiovascular disease (CVD) mortality in the elderly. OBJECTIVE: The objective of the study was to use prospective cohort study data to test whether the consumption of caffeinated beverages exhibits this protective effect. DESIGN: Cox regression analyses were conducted for 426 CVD deaths that occurred during an 8.8-y follow-up in the prospective first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. The analysis involved 6594 participants aged 32-86 y with no history of CVD at baseline. RESULTS: Participants aged >or=65 y with higher caffeinated beverage intake exhibited lower relative risk of CVD and heart disease mortality than did participants with lower caffeinated beverage intake. It was a dose-response protective effect: the relative risk (95% CI) for heart disease mortality was 1.00 (referent), 0.77 (0.54, 1.10), 0.68 (0.49, 0.94), and 0.47 (0.32, 0.69) for <0.5, 0.5-2, 2-4, and >or=4 servings/d, respectively (P for trend = 0.003). A similar protective effect was found for caffeine intake in mg/d. The protective effective was found only in participants who were not severely hypertensive. No significant protective effect was found in participants aged <65 y or in cerebrovascular disease mortality for those aged >or=65 y. CONCLUSION: Habitual intake of caffeinated beverages provided protection against the risk of heart disease mortality among elderly participants in this prospective epidemiologic analysis.

Repetitive monomorphic ventricular tachycardia associated with exercise--a case report.

The case of a 45-year-old man suffering from a catecholamine-sensitive ventricular tachycardia originating from the right ventricular outflow tract is reported. The authors describe a novel noninvasive treatment strategy for the management of this patient.

Usefulness of P-wave morphology during submaximal treadmill exercise to predict coronary artery disease.

Standard electrocardiographic criteria for exercise testing require near maximal exertion and fail to detect ischemia in the presence of previous infarction or conduction or repolarization abnormalities, in women, or in the presence of certain drugs. Changes in P-wave morphology have been suggested as having diagnostic utility; however, no specific criteria exist, and it is not clear which changes are most useful. This investigation evaluated the ability to detect the presence of coronary artery disease by examining changes in P-wave morphology during exercise. A group of 123 consecutive patients underwent maximum (symptom-limited) exercise nuclear stress tests. The electrocardiograms at rest, 2 minutes of exercise, 50% of maximum exercise time, maximum exercise, and 3 minutes of recovery were analyzed for the duration of the P wave in lead II, the duration of the terminal negative component of the P wave in lead V1, the amplitude of the terminal negative component of the P wave in lead V1, and the duration of the P wave in lead V5. These variables were then analyzed for their relation to the presence of perfusion defects. Of all the P-wave criteria tested, a change in amplitude of the negative component of the P wave in lead V1 from at rest to 50% of maximum exercise time of <0.025 mV was the most predictive of coronary artery disease.

Using RPE to regulate exercise intensity during a 20-week training program for postmenopausal women: a pilot study.

Feelings of effort sense quantified via the Borg Rating of Perceived Exertion (RPE) scale have been validated for regulating exercise intensity. Most studies validating RPE for exercise prescription have used young, male subjects and only a few exercise sessions. As part of a larger study we examined the accuracy of RPE for regulating exercise intensity in a group of postmenopausal women. Six women (70.0+/-7.1 yr.) were given a maximal graded exercise test. Target RPEs equivalent to 40%, 50% and 60% VO2 max were developed from this test using standard techniques. These RPEs were used to regulate intensity during a 20-wk. training program. During the initial 5 wk. of training target intensity was increased from 40% to 60% VO2 max and exercise duration from 15 to 30 min. Accuracy of exercise intensity regulation was determined by comparing the heart rate during exercise to a target heart rate equivalent to the desired %VO2 max. At Week 2 of training (target 40% VO2 max) the mean intensity produced did not differ from target. During Weeks 4 (target 50% VO2 max), 6 and 10 of training (target 60% VO2 max) the mean exercise intensity was below target. At Week 20 the mean intensity produced was not different from target. This suggests that elderly women can accurately use RPE to regulate exercise intensity, but at intensities above 40% VO2 max an acclimation period is needed.

Effect of naloxone on perceived exertion and exercise capacity during maximal cycle ergometry.

We assessed the effects of naloxone, an opioid antagonist, on exercise capacity in 13 men and 5 women (mean age = 30.1 yr, range = 21-35 yr) during a 25 W/min incremental cycle ergometer test to exhaustion on different days during familiarization trial and then after 30 mg (iv bolus) of naloxone or placebo (Pl) in a double-blind, crossover design. Minute ventilation (Ve), O(2) consumption (Vo(2)), CO(2) production, and heart rate (HR) were monitored. Perceived exertion rating (0-10 scale) and venous samples for lactate were obtained each minute. Lactate and ventilatory thresholds were derived from lactate and gas-exchange data. Blood pressure was obtained before exercise, 5 min postinfusion, at maximum exercise, and 5 min postexercise. There were no control-Pl differences. The naloxone trial demonstrated decreased exercise time (96% Pl; P < 0.01), total cumulative work (96% Pl; P < 0.002), peak Vo(2) (94% Pl; P < 0.02), and HR (96% Pl; P < 0.01). Other variables were unchanged. HR and Ve were the same at the final common workload, but perceived exertion was higher (8.1 +/- 0.5 vs. 7.1 +/- 0.5) after naloxone than Pl (P < 0.01). The threshold for effort perception amplification occurred at approximately 60 +/- 4% of Pl peak Vo(2). Thus we conclude that peak work capacity was limited by perceived exertion, which can be attenuated by endogenous opioids rather than by physiological limits.