Effects of prolonging peak dobutamine dose during stress echocardiography

Complications of exercise and pharmacologic stress echocardiography

Stress echocardiography is a diagnostic cardiovascular exam that is commonly utilized for multiple indications, including but not limited to the assessment of obstructive coronary artery disease, valvular disease, obstructive hypertrophic cardiomyopathy, and diastolic function. Stress echocardiography can be performed via both exercise and pharmacologic modalities. Exercise stress is performed with either treadmill or bicycle-based exercise. Pharmacologic stress is performed via either dobutamine or vasodilator-mediated (i.e., dipyridamole, adenosine) stress testing. Each of these modalities is associated with a low overall prevalence of major, life-threatening adverse outcomes, though adverse events are most common with dobutamine stress echocardiography. In light of the recent COVID-19 pandemic, the risk of infectious complications to both the patient and stress personnel cannot be negated; however, when certain precautions are taken, the risk of infectious complications appears minimal. In this article, we review each of the stress echocardiographic modalities, examine major potential adverse outcomes and contraindications, assess the risks of stress testing in the setting of a global pandemic, and examine the utilization and safety of stress testing in special patient populations (i.e., language barriers, pediatric patients, pregnancy).

Right ventricular pressure dynamics and stress echocardiography in pharmacological and exercise stress testing

REASONS FOR PERFORMING STUDY

There is interest in using pharmacological stress testing (PST) as a substitute for exercise stress testing (EST) to evaluate cardiac function in horses.

OBJECTIVES

To compare the effect of PST and EST on right ventricular pressure dynamics and stress echocardiography.

METHODS

Five horses completed a PST and EST in a randomised crossover design. High fidelity pressure transducers were placed in the right ventricle. Continuous pressure signals were digitally collected and stored, and dP/dtmax, dP/dtmin and tau calculated from these measurements. ECGs were recorded continuously for 20 h. Echocardiography was performed prior to EST and PST, during and after PST, and immediately post EST. Plasma cardiac troponin I concentrations were measured pre- and 3-4 h post stress testing. For PST, 5 microg/kg bwt glycopyrrolate i.v. followed after 10 min by 5 microg/kg bwt/min dobutamine infusion over 10 min was given. EST consisted of a 2 min gallop at 110% speed required to elicit VO2max.

RESULTS

Both EST and PST resulted in a significant increase in right-ventricular dP/dtmax and dP/dtmin over baseline (P<0.05) and a significant decrease in tau compared with baseline (P<0.05). EST dP/dtmax and dP/dtmin were significantly greater than PST dP/dtmax and dP/dtmin (P<0.05) and EST tau was significantly less than PST tau (P<0.05). Two minutes post EST and 5 min post PST dP/dtmax were not significantly different, but were significantly less than end-EST and during PST. Tau was also not significantly different between post EST and post PST, but was significantly decreased end-EST compared with during PST. FS were not significantly different between PST and post EST, but during PST and post EST all FS were significantly higher than baseline. Cardiac troponin I concentrations were significantly elevated post PST and were greater than post EST. The clinical relevance of this is unknown.

CONCLUSIONS

PST had a similar, although less marked effect on the cardiac parameters related to right-ventricular pressure dynamics and a similar effect on echocardiography as exercise stress testing.

POTENTIAL RELEVANCE

PST deserves further evaluation in normal horses and those with cardiac disease, and may be complementary to EST to better identify exercise-induced cardiac dysfunction.

Accelerated dobutamine stress testing: safety and feasibility in patients with known or suspected coronary artery disease

BACKGROUND

Dobutamine pharmodynamics require approximately 10 min to reach steady state. Despite this, standard dobutamine stress echo typically uses 3-min stages of advancing dobutamine doses because of safety concerns.

HYPOTHESIS

In patients with a high pretest probability of coronary artery disease (CAD), a continuous infusion of high-dose dobutamine is a feasible and safe method for performing a dobutamine stress test.

METHODS

Forty-seven consecutive patients (mean age 64 +/- 11 years) with 3.0 +/- 1.4 cardiac risk factors underwent dobutamine stress testing utilizing a single, high-dose (40 mcg/kg/min), continuous dobutamine infusion. The 40 mcg/kg/min infusion was continued for up to 10 min or until a test endpoint had been reached. If a test endpoint was not achieved, atropine (up to 1.0 mg) was added.

RESULTS

Heart rate rose from 71 +/- 12 to 137 +/- 18 beats/min at peak (p<0.0001) with a concomitant change in systolic blood pressure (143 +/- 35 vs. 167 +/- 38 mmHg; p = 0.001) but no change in diastolic blood pressure (74 +/- 19 vs. 75 +/- 18 mmHg; p = NS). Target heart rate was achieved in 20 of 47 (43%) patients with accelerated dobutamine alone and in 34 of 47 (72%) with the addition of atropine. An average of 11.6 +/- 3.7 min was required to obtain target heart rate. Subjective sensations from the dobutamine occurred in 49% of patients (palpitations 21%, nausea 6%, chest pain 6%, headache 6%, dizziness 13%), mild arrhythmia in 48% of patients (ventricular premature beats 38%, supraventricular tachycardia 10%), and one patient had nonsustained ventricular tachycardia.

CONCLUSION

A single, high-dose (40 mcg/kg/min) dobutamine-atropine protocol provides an efficient means of performing dobutamine stress echocardiography with a similar symptom profile as conventional dobutamine infusion protocols in patients with a high pretest probability of CAD. Randomized, controlled studies will be necessary to assess the sensitivity and specificity of this accelerated dobutamine echo protocol.

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.

The effects of early administration of atropine during dobutamine stress echocardiography: advantages and disadvantages of early dobutamine-atropine protocol

Background

The conventional dobutamine protocol for the investigation of induced myocardial ischemia is well established. Our objective was to evaluate the effects of early administration of atropine during the dobutamine stress echocardiogram, as compared to its conventional use.

Methods

One hundred and twenty-one patients were referred to the dobutamine stress echocardiogram, for the investigation of myocardial ischemia and the administration of atropine was randomized into three groups (A, B, C at 10, 20 and 40 mcg/kg/min of dobutamine, respectively).

Results

The mean level of the double product was significantly lower in the group C patients when compared to group B patients (p = 0.002). The mean test time (12.8 ± 3.1 and 18.7 ± 3.4 p= 0.0001) and the mean total dose of dobutamine (14 × 18 × 25 mg p = 0.008) were significantly higher in group C patients than in group A & B patients. The mean test time was reduced in 6 minutes (31%) with the early administration of atropine in relation to the standard protocol. The atropine dose used in the different groups was similar. Complications were uniform in all cases.

Conclusion

The early administration of atropine during the dobutamine-atropine stress echocardiography significantly reduces duration of the test and the dose of amine without increasing the number of complications, the total dose of atropine or the number of diagnostic tests.

Evaluation of the hemodynamic performance of St. Jude mitral prostheses: a pilot study by dobutamine-stress Doppler echocardiography

In contrast to the widespread use of dobutamine stress Doppler echocardiography in the hemodynamic evaluation of the prosthetic valves in aortic position, it has been rarely, if ever, used for assessment of these valves in mitral position. Therefore, this pilot study was done to assess the hemodynamic performance of St. Jude prosthetic mitral valves (functional orifice area 25-31) with dobutamine-stress Doppler echocardiography. Twenty consecutive patients (13 women and 7 men, aged 23 to 42 years) who had undergone mitral valve replacement 6 to 4745 days previously and 16 healthy volunteers (5 women and 11 men, aged 18 to 42 years) underwent dobutamine-stress Doppler echocardiography. Dobutamine infusion was started at a rate of 5 microg/kg per minute and was increased by 5 microg increments at 3-minute intervals. Maximum and mean gradients as well as pressure halftime were measured at rest and at the end of each stage. The correlation between Doppler-derived variables versus the heart rate was assessed and a regression equation was obtained for each of them. A significant increase in blood pressure, heart rate, maximum and mean gradients was noted during dobutamine infusion in both groups. There was a significant positive linear correlation between the increasing transprosthetic mitral valvular maximum and mean gradients and the increments in the heart rate (G(max) = 4.47 + 0.093 [HR], r= 0.474, p<0.05) and (G(mean) = 3.0+0.003 [HR], r=0.2697, p<0.05), respectively, indicating the heart rate dependency of these parameters. Pressure halftime, on the other hand, had an inverse but linear relationship with the heart rate (PHT = 142 - 0.55 [HR], r= -0.577, p<0.05). Similar findings were found for the control group as well. Standard dobutamine-stress echocardiography can safely be performed in patients with St. Jude mitral valve prostheses. Single Doppler measurements of the pressure gradients and pressure halftime may yield erroneous conclusions regarding the function and size of these valves unless corrected for the patients simultaneous, online heart rate. The use of the regression equations obtained in this pilot study may help to partly overcome some of these difficult issues.

Intracoronary ultrasound in acute coronary syndromes: from characterization of vulnerable plaques to guidance of percutaneous treatment of complex stenoses

Our current knowledge on the substrate and genesis of acute coronary syndromes (ACS) results from the integration of pathological, angiographic, and intracoronary imaging techniques. To summarize briefly the current paradigm, eight differentiated stages of development of atherosclerotic lesions are currently accepted, defined not only by the cellular elements involved, but also by the appearance of sudden alterations of plaque structure and coronary thrombosis. The latter constitutes not only the dominant substrate for the most devastating manifestations of coronary artery disease, but also accelerates plaque size at a faster pace than in earlier stages. The composition of atherosclerotic plaque varies significantly along the different evolutive stages, and thus includes cellular (macrophage, smooth muscle cells) and noncellular elements (glicosaminglycan or collagen-rich cellular matrix, extracellular lipid deposits, calcification, fresh, or organized thrombus) in a varying proportion. Furthermore, a dynamic process of vessel remodeling occurs along the atherosclerotic process, resulting, in most cases, in a protective mechanism against myocardial ischemia by preserving luminal dimensions during plaque enlargement. Intravascular ultrasound (IVUS) is one of the intracoronary imaging techniques that has contributed to the understanding of these changes in man. In addition, IVUS has the potential of being a useful clinical tool for predicting the chances of future acute coronary events by identifying vulnerable plaques, of characterizing which is the culprit lesion in ACS, and in guiding revascularization procedures in the treacherous field of thrombotic coronary syndromes. In this article, we review the current evidence on the potential of IVUS imaging for fulfilling these purposes.

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.

Left atrial appendage: structure, function, and role in thromboembolism

The left atrial appendage (LAA) is derived from the left wall of the primary atrium, which forms during the fourth week of embryonic development. It has developmental, ultrastructural, and physiological characteristics distinct from the left atrium proper. The LAA lies within the confines of the pericardium in close relation to the free wall of the left ventricle and thus its emptying and filling may be significantly affected by left ventricular function. The physiological properties and anatomical relations of the LAA render it ideally suited to function as a decompression chamber during left ventricular systole and during other periods when left atrial pressure is high. These properties include the position of the LAA high in the body of the left atrium; the increased distensibility of the LAA compared with the left atrium proper; the high concentration of atrial natriuretic factor (ANF) granules contained within the LAA; and the neuronal configuration of the LAA. Thrombus has a predilection to form in the LAA in patients with atrial fibrillation, mitral valve disease, and other conditions. The pathogenesis has not been fully elucidated; however, relative stasis which occurs in the appendage owing to its shape and the trabeculations within it is thought to play a major role. Obliteration or amputation of the LAA may help to reduce the risk of thromboembolism, but this may result in undesirable physiological sequelae such as reduced atrial compliance and a reduced capacity for ANF secretion in response to pressure and volume overload.

Pharmacologic stress echocardiography. Dobutamine and arbutamine stress testing

Pharmacologic stress testing is an important noninvasive method for evaluating patients with known or suspected coronary artery disease who are unable to adequately exercise. Pharmacologic stress echocardiography using dobutamine has been developed over the last 10 to 15 years as an alternative to vasodilator stress testing using nuclear perfusion imaging. As experience has grown, digital subtraction echocardiogram has been shown to be a safe, convenient, and reliable method for stress testing in a variety of patient populations. Digital subtraction echocardiogram has comparable sensitivity, specificity, and accuracy when compared to other stress testing methods which employ cardiac imaging and is superior to the exercise echocardiogram. It has certain advantages over nuclear perfusion imaging in terms of cost and convenience. The recent addition of arbutamine echocardiography (which has been shown to be comparable to digital subtraction echocardiogram) provides another alternative method for pharmacologic stress testing. Continued improvement in echocardiographic image quality and the development of new technologies such as tissue harmonic imaging and contrast echocardiography will hopefully improve the echocardiographic evaluation of wall motion therefore increasing the diagnostic accuracy of echocardiographic stress testing.

Review: Clinical aspects of vascular remodeling

Vascular remodeling represents a spectrum of structural changes whereby the vascular wall responds to changes in its hemodynamic environment. Such changes may be classified as vessel enlargement (outward remodeling), diminution (inward remodeling), alternatively as adaptive (compensatory, appropriate to the hemodynamic stimulus), or maladaptive (dysfunctional, inappropriate). The direction and scale of remodeling are coordinated by endothelial production of growth factors, proteases, and cellular adhesion molecules in response to sensed changes in blood flow. In early atherosclerosis, outward remodeling preserves lumen size. Although protective in the long-term, the matrix degradation involved in this process may predispose atherosclerotic plaques to rupture, hence increasing the risks of acute coronary syndromes. Inward remodeling also occurs in advanced atherosclerotic lesions, whereby the vessel shrinks rather than enlarging, exacerbating rather than ameliorating stenosis. In transplant coronary artery disease, early inward remodeling may be a more important component of vessel stenosis than intimal thickening, while inappropriate inward remodeling appears to be as least as important as excessive intimal growth in the development of restenosis after angioplasty. Increased awareness of vascular remodeling, and in particular its malaptive forms, may provide new therapeutic insights for the future.

Usefulness of isometric hand grip exercise in detecting coronary artery disease during dobutamine atropine stress echocardiography in patients with either stable angina pectoris or another type of positive stress test

Dobutamine atropine stress echocardiography (DASE) detects coronary artery disease (CAD) by increasing myocardial oxygen demand causing ischemia. The sensitivity of the test for detection of CAD is reduced in patients with submaximal stress. We hypothesized that increasing cardiac work load by adding isometric exercise would improve the detection of ischemia during DASE. We studied 31 patients, mean age 57+/-11 years, with angiographically documented CAD. Patients underwent DASE using incremental dobutamine doses from 5 to 40 microg/kg/min, followed by atropine if peak heart rate was <85% of predicted maximal. Hand grip was then performed for 2 minutes at 33% of maximal voluntary contraction, while dobutamine infusion was maintained at the peak dose. The addition of hand grip during dobutamine stress was associated with a significant increase in systolic blood pressure (143+/-21 vs 164+/-24 mm Hg, p = 0.001) and left ventricular end-systolic circumferential wall stress (72+/-30 x 10(3) dynes/cm2 vs 132+/-34 x 10(3) dynes/cm2, p = 0.004). Wall motion score index increased from 1.0 at rest to 1.15+/-0.18 with dobutamine (p = 0.0004 vs rest), and increased further to 1.29+/-0.22 with the addition of hand grip (p = 0.004 vs dobutamine). Ischemia was detected in 19 patients (62%) with dobutamine-atropine stress alone and in 25 (83%) after the addition of hand grip (p <0.05). The addition of hand grip during DASE is feasible, and improves the detection of myocardial ischemia.

Reduced test time by early identification of patients requiring atropine during dobutamine stress echocardiography

In a randomized, controlled clinical trial, we evaluated the ability of an algorithm to identify, before peak stress, patients who will ultimately require atropine during dobutamine stress echocardiography. The effects of early atropine administration on test duration, atropine dose, dobutamine dose, and heart rate response also were studied. Compared with conventional atropine administration at peak dobutamine infusion, early atropine administration reduced test duration 8% (1.1 minutes, p = 0.02) and total dobutamine use 11% (0.41 mg/kg, p = 0.02) but required 90% more atropine (0.36 mg, p < 0.001). Conventional atropine administration resulted in a late, rapid rise in both heart rate and rate-pressure product. However, the heart rate and rate-pressure product curves for patients receiving early atropine paralleled those seen in patients not requiring atropine during dobutamine stress echocardiography. In conclusion, early atropine administration provides a more balanced stress and reduces test duration, thus decreasing total exposure to dobutamine and potentially increasing test efficiency.

Usefulness of isometric exercise during dobutamine administration for stress echocardiography

An isometric exercise was performed by 170 consecutive patients at peak dose dobutamine, before atropine administration. The test was well tolerated, heart rate increased significantly during exercise, and atropine administration was avoided in 29% of patients.