Pharmacologic stress echocardiography. Dobutamine and arbutamine stress testing

Dobutamine-induced complete heart block

Dobutamine is commonly administered as a pharmacologic stressor in patients with limitations precluding exercise testing. The case report presented is one of transient complete heart block resulting from dobutamine sestamibi stress testing. Shortly after initiating the dobutamine infusion, the patient became pale and presyncopal, with hypotension and a heart rate of 50 beats per minute. Subsequently, third-degree heart block developed which lasted transiently and resolved. Subsequent cardiac evaluation of the patient revealed no cardiac etiology for her symptoms. Though bradycardia is infrequently noted in patients receiving dobutamine during stress electrocardiogram, complete heart block is a possibility during dobutamine-induced stress echocardiography and must be recognized as a potential risk.

Feasibility, safety and tolerability of accelerated dobutamine stress echocardiography

A continuous infusion of a single high dose of dobutamine has been, recently, suggested as a simple and effective protocol of stress echocardiography. The present study assesses the feasibility, safety, and tolerability of an accelerated dobutamine stress protocol performed in patients with suspected or known coronary artery disease. Two hundred sixty five consecutive patients underwent accelerated dobutamine stress echocardiography: the dobutamine was administered at a constant dose of 50 μg/kg/min for up to 10 minutes. The mean weight-adjusted cumulative dose of dobutamine used was 330 ± 105.24 μg/kg. Total duration of dobutamine infusion was 6.6 ± 2.1 min. Heart rate rose from 69.9 ± 12.1 to 123.1 ± 22.1 beats/min at peak with a concomitant change in systolic blood pressure (127.6 ± 18.1 vs. 167.6 ± 45.0 mmHg). Dobutamine administration produced a rapid increase in heart rate (9.4 ± 5.9 beats/min²). The side effects were similar to those described with the standard protocol; the most common were frequent premature ventricular complexes (21.5%), frequent premature atrial complexes (1.5%) and non sustained ventricular tachycardia (1.5%); among non cardiac symptoms the most frequent were nausea (3.4%), headache (1.1%) and symptomatic hypotension (1.1%). No major side effects were observed during the test. Our data demonstrate that a continous infusion of a single high dose of dobutamine is a safe and well tolerated method of performing stress echocardiography in patients with suspected or known coronary artery disease. This new protocol requires the administration of lower cumulative dobutamine dose than standard protocol and results in a significant reduction in test time.

Cardiovascular physiology during supine cycle ergometry and dobutamine stress

PURPOSE

This study compared cardiac hemodynamics during supine cycle ergometry and dobutamine stress.

METHODS

Thirty-two healthy volunteers (19 female, 13 male, 23.5 +/- 3.5 yr old) completed respective tests on separate days and in random order. Heart rate, blood pressure, and cardiac output were recorded at baseline and peak stress. Echocardiographic measures included left ventricular end-diastolic dimension, fractional shortening, heart rate corrected velocity of circumferential fiber shortening, end-systolic wall stress, and the difference between measured and predicted fiber shortening for measured wall stress.

RESULTS

Compared with peak exercise, dobutamine infusion resulted in lower cardiac output (12 +/- 2 vs 16 +/- 4 l x min(-1), P < 0.0001), heart rates (163 +/- 7 vs 175 +/- 12 beats x min(-1), P < 0.0001), and systolic blood pressure (160 +/- 22 vs 185 +/- 20 mm Hg, P < or = 0.0001). Echocardiography demonstrated smaller left ventricular end-diastolic dimension (4.2 +/- 0.7 vs 4.5 +/- 0.7 cm, P = 0.013), higher fractional shortening (0.55 +/- 0.07 vs 0.50 +/- 0.06%, P < 0.001), higher VCFc (2.07 +/- 0.36 vs 1.54 +/- 0.20 circs x s(-1), P < 0.001) higher VCFdiff (0.94 +/- 0.35 vs 0.48 +/- 0.20 circs x s(-1), P < 0.001), and lower end-systolic wall stress (25 +/- 11 vs 42 +/- 16 g x cm(-2), P < 0.001). The stress-velocity relationship during dobutamine demonstrated higher y-intercept and steeper slope, indicating greater load-independent contractility.

CONCLUSION

The cardiovascular adaptation to exercise and dobutamine stress differ significantly. Cardiac output during peak exercise is greater than during peak dobutamine secondary to increased heart rate and stroke volume. Despite a greater increase in contractility and decrease in afterload, a smaller increase in cardiac output during dobutamine stress may be secondary to limited ventricular preload.

[Dobutamine stress test. Specificity and sensitivity of continuous ST-segment monitoring in 12 simultaneous standard ECG leads]

INTRODUCTION AND OBJECTIVES

This study was designed to evaluate the specificity and sensitivity of the dobutamine stress test with continuous ST-segment monitoring in 12 standard leads.

PATIENTS AND METHOD

We analyzed 75 patients, 36 with unstable angina, 22 post-myocardial infarction angina, 3 after successful angioplasty, 6 chronic stable angina, and 8 atypical chest pain (with normal coronary arteries). All of them underwent coronary angiography (coronary lesions were considering significant with > 70%). Beta-blocking agents, calcium antagonists, and nitrates were discontinued for 48 h before the test. A 12-lead ECG was acquired automatically and ST-segment changes were monitored. Dobutamine infusion started at 5 microgram/kg/min and was increased at 3-minute intervals to 10 microgram, 20 microgram, and a maximum of 40 microgram/kg/min. If heart rate did not reach 85% of the theoretical maximum, 0.5-1 mg atropine was given without discontinuing dobutamine infusion.

RESULTS

Fifty patients (67%) had abnormal coronary arteries (excluding vessels with 100% obstruction) and 25 patients (33%) had normal arteries. In the group of patients with coronary lesions, the test was abnormal in 90% and normal in 10%. In the group of patients with normal arteries, the test was abnormal in 16% and normal in 84%. Consequently, the test had 90% sensitivity, 84% specificity, and 10% false negative and 16% false positive results.

CONCLUSIONS

Our results showed that the dobutamine/ECG test was a simple, effective, and safe bedside tool for diagnosing the severity of coronary disease.

Pharmacological stress agents for evaluation of ischemic heart disease

Ischemic heart disease is the leading cause of death in the developed countries for those older than 65 years of age. In patients suspected to have coronary artery disease a stress test should be performed to identify the vulnerability of the myocardium to ischemia. As a rule of thumb, the evaluation of coronary artery disease is best done by exercise stress test. In patients who are not able to exercise adequately, pharmacological stress agents are used. The commonly used agents are the coronary vasodilators, adenosine and dipyridamole and the catecholamines, dobutamine and arbutamine. These agents are combined with imaging techniques to increase the sensitivity and specificity of the test. These agents have been widely used and have an excellent safety profile. Another advantage in using pharmacological stress agents is that they do not affect the image quality, especially with echocardiography and magnetic resonance imaging. Ongoing developments hold promise for safer and more reliable pharmacological stress agents in the future.

Safety and efficacy of an accelerated dobutamine stress echocardiography protocol in the evaluation of coronary artery disease

Although dobutamine requires up to 10 minutes to achieve steady state, dobutamine stress echocardiography is routinely performed using stepwise increments at 3-minute intervals. Consequently, the full effect of any infusion rate is not attained before the dobutamine dose is advanced to the next level. This study sought to test the safety and efficiency of high-dose continuous dobutamine infusion. One hundred consecutive patients underwent an accelerated protocol using a constant infusion of 50 microg/kg/min. In the absence of a stress echocardiographic end point (>/=85% of maximal predicted heart rate, new wall motion abnormalities, hypotension, arrhythmia, or intolerable symptoms), dobutamine infusion was discontinued at 10 minutes. Hemodynamic responses and adverse effect profile were compared with 100 patients who underwent a standard stepwise dobutamine stress protocol. Peak heart rate (140 +/- 16 vs 140 +/- 19 beats/min, p = 0.95) and systolic blood pressure (169 +/- 32 vs 162 +/- 31 mm Hg, p = 0.08) were similar in both protocols. Accelerated dobutamine administration produced a rapid increase in heart rate (12.5 +/- 6.2 vs 5.7 +/- 2.6 beats/min, p <0.001), and a substantial reduction in test duration (6.4 +/- 2.4 vs 12.9 +/- 3.0 minutes, p <0.001). The mean weight-adjusted cumulative dobutamine dose was lower in the accelerated protocol group (320 +/- 111 vs 353 +/- 133 microg/kg, p = 0.016). No significant differences were noted between the 2 groups with respect to various side effects. These data demonstrate that a high-dose, single-stage dobutamine echocardiographic stress protocol is a feasible, well-tolerated alternative to standard dobutamine stress echocardiography, and results in a substantial reduction in test time while maintaining a low complication rate.