Withholding or continuing beta-blocker treatment before dipyridamole myocardial perfusion imaging for the diagnosis of coronary artery disease? A randomized clinical trial

Effect of Beta-Blocker Consumption on the Severity and Extension of Perfusion Defects in Dipyridamole Myocardial Perfusion Single-Photon Emission Computed Tomography

Background  Regarding the less-known effects of beta-blocker consumption on the diagnostic value of the myocardial perfusion scan with dipyridamole stress in coronary artery disease (CAD), we aimed to compare the findings of the scans done on the beta-blocker consumption course and after discontinuation of this medications. Materials and Methods  Thirty patients with probably CAD and abnormal myocardial perfusion scans (presence of reversible defect), who had been treated with beta-blockers for at least 3 months, were studied. Dipyridamole stress phase of myocardial perfusion single-photon emission computed tomography (SPECT) was performed two times with an interval of about 1 week, once after discontinuation of all antianginal and anti-ischemic medications, statins, and beta-blockers for 72 hours prior to the study, and again after discontinuation of all these medications except for beta-blockers. Imaging was done with the same protocol, radiopharmaceutical dose, and imaging parameters. Summed stress score (SSS), summed stress rest, and summed difference scores (SDS), total perfusion deficit (TPD), severity, and extension of myocardial perfusion defects in three coronary artery territories were analyzed, using quantitative perfusion SPECT software. Results  Most variables such as SSS, SDS, TPD, severity, and extension of defects showed a significant difference between the two conditions including beta-blocker consumption and after discontinuing beta-blocker consumption before stress imaging ( p  < 0.05). Moreover, in patients on treatment with metoprolol, all studied factors including SSS, SDS, TPD, severity, and extension of perfusion defects were significantly reduced when patients consumed beta-blockers before SPECT evaluation ( p  < 0.05). Conclusion  Beta-blocker consumption can lead to a decrease in the severity and extent of myocardial perfusion defects and therefore probably a decrease in the sensitivity of myocardial scans. Discontinuation of beta-blocker prior to the dipyridamole myocardial perfusion scan can improve diagnostic accuracy.

Technical Considerations for Dynamic Myocardial Computed Tomography Perfusion as Part of a Comprehensive Evaluation of Coronary Artery Disease Using Computed Tomography

Dynamic myocardial computed tomography perfusion (DM-CTP) has good diagnostic accuracy for identifying myocardial ischemia as compared with both invasive and noninvasive reference standards. However, DM-CTP has not yet been implemented in the routine clinical examination of patients with suspected or known coronary artery disease. An important hurdle in the clinical dissemination of the method is the development of the DM-CTP acquisition protocol and image analysis. Therefore, the aim of this article is to provide a review of critical parameters in the design and execution of DM-CTP to optimize each step of the examination and avoid common mistakes. We aim to support potential users in the successful implementation and performance of DM-CTP in daily practice. When performed appropriately, DM-CTP may support clinical decision making. In addition, when combined with coronary computed tomography angiography, it has the potential to shorten the time to diagnosis by providing immediate visualization of both coronary atherosclerosis and its functional relevance using one single modality.

By discontinuing beta-blockers before an exercise test we may precipitate a rebound phenomenon

BACKGROUND

There is a need to analyse the current approach to beta-blocker (BB) use in relation to exercise-based stress tests.

OBJECTIVE

We compared various guidelines regarding recommending abrupt vs gradual discontinuation of BB prior to exercise tests. We also analyse the shortcomings of the currently recommended approach and suggest a new approach to avoid BB rebound.

METHODS

A narrative review is used to analyse this topic due to lack of valid randomized clinical trials.

RESULTS

Omitting the BB therapy prior to exercise-based test has been recommended in guidelines for many years. Although reasonable, this approach has potential disadvantages since sudden BB withdrawal may induce a rebound phenomenon, which is, also, acknowledged in several guidelines.

CONCLUSIONS

We observed inconsistency among relevant guidelines; there is no homogenous approach regarding BB use before exercise tests. Most guidelines recommend BB withdrawal for a couple of days before the test; they do not advise BB dose tapering. This approach is not standardised and raises the risk of BB rebound phenomenon both before and during the test. Therefore, we suggest using the half the prescribed BB dose at the usual time of administration (in the morning, prior to the exercise test).

Expiratory Flow Limitation at Different Exercise Intensities in Coronary Artery Disease

Introduction

Expiratory flow limitation (EFL) during moderate intensity exercise is present in patients with myocardial infarction (MI), whereas in healthy subjects it occurs only at a high intensity. However, it is unclear whether this limitation already manifests in those with stable coronary artery disease (CAD) (without MI).

Materials and Methods

Forty-one men aged 40–65 years were allocated into (1) recent MI (RMI) group (n = 8), (2) late MI (LMI) group (n = 12), (3) stable CAD group (n = 9), and (4) healthy control group (CG) (n = 12). All participants underwent two cardiopulmonary exercise tests at a constant workload (moderate and high intensity), and EFL was evaluated at the end of each exercise workload.

Results

During moderate intensity exercise, the RMI and LMI groups presented with a significantly higher number of participants with EFL compared to the CG (p < 0.05), while no significant difference was observed among groups at high intensity exercise (p > 0.05). Moreover, EFL was only present in MI groups during moderate intensity exercise, whereas at high intensity all groups presented EFL. Regarding the degree of EFL, the RMI and LMI groups showed significantly higher values at moderate intensity exercise in relation to the CG. At high intensity exercise, significantly higher values for the degree of EFL were observed only in the LMI group.

Conclusion

The ventilatory limitation at moderate intensity exercise may be linked to the pulmonary consequences of the MI, even subjects with preserved cardiac and pulmonary function at rest, and not to CAD per se.

Hyperventilation-induced heart rate response as a potential marker for cardiovascular disease

An increase of heart rate to physical or mental stress reflects the ability of the autonomous nervous system and the heart to respond adequately. Hyperventilation is a user-controlled breathing maneuver that has a significant impact on coronary function and hemodynamics. Thus, we aimed to investigate if the heart rate response to hyperventilation (HRRHV) can provide clinically useful information. A pooled analysis of the HRRHV after 60 s of hyperventilation was conducted in 282 participants including healthy controls; patients with heart failure (HF); coronary artery disease (CAD); a combination of both; or patients suspected of CAD but with a normal angiogram. Hyperventilation significantly increased heart rate in all groups, although healthy controls aged 55 years and older (15 ± 9 bpm) had a larger HRRHV than each of the disease groups (HF: 6 ± 6, CAD: 8 ± 8, CAD+/HF+: 6 ± 4, and CAD-/HF-: 8 ± 6 bpm, p < 0.001). No significant differences were found between disease groups. The HRRHV may serve as an easily measurable additional marker of cardiovascular health. Future studies should test its diagnostic potential as a simple, inexpensive pre-screening test to improve patient selection for other diagnostic exams.

Circulatory and Ventilatory Power: Characterization in Patients with Coronary Artery Disease

Background

Circulatory power (CP) and ventilatory power (VP) are indices that have been used for the clinical evaluation of patients with heart failure; however, no study has evaluated these indices in patients with coronary artery disease (CAD) without heart failure.

Objective

To characterize both indices in patients with CAD compared with healthy controls.

Methods

Eighty-seven men [CAD group = 42 subjects and healthy control group (CG) = 45 subjects] aged 40–65 years were included. Cardiopulmonary exercise testing was performed on a treadmill and the following parameters were measured: 1) peak oxygen consumption (VO₂), 2) peak heart rate (HR), 3) peak blood pressure (BP), 4) peak rate-pressure product (peak systolic HR x peak BP), 5) peak oxygen pulse (peak VO₂/peak HR), 6) oxygen uptake efficiency (OUES), 7) carbon dioxide production efficiency (minute ventilation/carbon dioxide production slope), 8) CP (peak VO₂ x peak systolic BP) and 9) VP (peak systolic BP/carbon dioxide production efficiency).

Results

The CAD group had significantly lower values for peak VO₂ (p < 0.001), peak HR (p < 0.001), peak systolic BP (p < 0.001), peak rate-pressure product (p < 0.001), peak oxygen pulse (p = 0.008), OUES (p < 0.001), CP (p < 0.001), and VP (p < 0.001) and significantly higher values for peak diastolic BP (p = 0.004) and carbon dioxide production efficiency (p < 0.001) compared with CG. Stepwise regression analysis showed that CP was influenced by group (R² = 0.44, p < 0.001) and VP was influenced by both group and number of vessels with stenosis after treatment (interaction effects: R² = 0.46, p < 0.001).

Conclusion

The indices CP and VP were lower in men with CAD than healthy controls.

Advances in stress cardiac MRI and computed tomography

Stress cardiac MRI and stress computed tomography (CT) perfusion are relatively new, noninvasive cardiovascular stress-testing modalities. Both of these tests have undergone rapid technical improvements. Data from randomized controlled trials in stress cardiac MRI are becoming gradually incorporated into cardiovascular clinical practice, not only to assess physiological significance of coronary artery disease, but also to provide prognostic information. As CT perfusion protocols become more uniform with adequate handling of artifacts and decreasing radiation exposure with combined CT coronary angiography/CT perfusion imaging, it has the potential to become a comprehensive diagnostic test.