Sustained reduction of exercise perfusion defect extent and severity with isosorbide mononitrate (Imdur) as demonstrated by means of technetium 99m sestamibi

Medication and ECG Patterns That May Hinder SPECT Myocardial Perfusion Scans

Coronary artery disease (CAD) is the leading cause of death followed by cancer, in men and women. With risk factors being endemic and the increasing costs of healthcare for management and treatment, myocardial perfusion imaging (MPI) finds a central role in risk stratification and prognosis for CAD patients, but it comes with its limitations in that the referring clinician and managing team must be aware of and use at their advantage. This narrative review examines the utility of myocardial perfusion scans in the diagnosis and management of patients with ECG alterations such as atrioventricular block (AVB), and medications including calcium channel blockers (CCB), beta blockers (BB), and nitroglycerin which may impact the interpretation of the exam. The review analyzes the current evidence and provides insights into the limitations, delving into the reasons behind some of the contraindications to MPI.

Fragmented QRS on 12-Lead Electrocardiogram Is Correlated With Severe Coronary Artery Disease and Abnormal Myocardial Perfusion Scintigraphy Results in Renal Transplant Candidates

OBJECTIVES

Coronary artery disease is a major cause of mortality and morbidity after renal transplant. Fragmented QRS on standard 12-lead electrocardiograms has been proposed as a marker of myocardial scar, mainly due to coronary artery disease. Here, we aimed to investigate fragmented QRS to detect severe coronary artery disease in renal transplant candidates.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 534 patients with end-stage renal failure who were on the deceased-donor renal transplant wait list at Başkent University Faculty of Medicine due to having no living kidney donor available. We evaluated patients with standard 12-lead electrocardiograms, myocardial perfusion scintigraphy, and coronary angiography. We compared fragmented QRS prevalence versus myocardial perfusion scintigraphy abnormalities and severe coronary artery disease. Correlations among these were analyzed.

RESULTS

Of 92 renal transplant candidates (median age of 56.5 y; range, 24-80 y), 87 patients (94.6%) had myocardial perfusion defects and 72 (78.3%) had myocardial wall motion abnormalities on myocardial perfusion scintigraphy. Forty-four patients (47.8%) had severe coronary artery disease on coronary angiography, and 51 patients (55.4%) had fragmented QRS. Fragmented QRS was significantly more common among patients with myocardial scar. Coronary artery disease was significantly more common in patients with fragmented QRS (P = .042) and in those with fragmented QRS combined with myocardial perfusion defects (P < .01). Fragmented QRS was significantly correlated with presence of myocardial scar and any perfusion defects. When combined with myocardial perfusion defects, fragmented QRS was significantly correlated with severe coronary artery disease (P < .05).

CONCLUSIONS

Fragmented QRS was significantly correlated with abnormal myocardial perfusion scintigraphy and severe coronary artery disease in renal transplant candidates. This simple parameter can provide valuable information on severe coronary artery disease and help to prevent excess patient morbidity and mortality from this disease after renal transplant.

Coronary microvascular dysfunction in patients with stable coronary artery disease: The CE-MARC 2 coronary physiology sub-study

BACKGROUND

In patients with angina undergoing invasive management, no obstructive coronary artery disease (NOCAD) is a common finding, and angina may persist following percutaneous coronary intervention (PCI). Coronary microvascular dysfunction may be relevant. We aimed to assess the proportion of patients presenting with suspected CAD who had coronary microvascular dysfunction.

METHODS

Clinical Evaluation of Magnetic Resonance Imaging in Coronary Heart Disease 2 (CE-MARC 2) was a prospective multicenter randomised controlled trial of functional imaging versus guideline-based management in patients with suspected CAD. Invasive coronary angiography was protocol-directed. Fractional flow reserve (FFR) and parameters of microvascular function (coronary flow reserve (CFR), index of microcirculatory resistance (IMR), resistance reserve ratio (RRR)) were measured in major epicardial coronary arteries with ≥40-≤90% diameter stenosis. An FFR value ≤0.80 indicated the presence of obstructive CAD.

RESULTS

267/1202 (22.2%) patients underwent angiography and 81 (30%) patients had FFR measured. 63 (78%) of these patients had microvascular function assessed in 85 arteries (mean age 58.5 ± 8.2 years; 47 (75%) male). 25/63 (40%) patients had NOCAD, and of these, 17 (68%) had an abnormality ≥1 parameter of microvascular function (abnormal IMR (≥25), abnormal CFR (<2.0), and abnormal RRR (<2.0) occurred in 10 (40%), 12 (48%), and 11 (44%), respectively). 38/63 (60%) patients had obstructive epicardial CAD. Of these patients, 15/38 (39%), 20/38 (53%), and 12/38 (32%) had an abnormal IMR, CFR and RRR, respectively.

CONCLUSIONS

Coronary microvascular dysfunction is common in patients with angina. Invasive assessment of microvascular function may be informative and relevant for decision-making in patients with both NOCAD and obstructive epicardial CAD.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01664858.

Vasodilator Therapy: Nitrates and Nicorandil

Nitrates have been used to treat symptoms of chronic stable angina for over 135 years. These drugs are known to activate nitric oxide (NO)-cyclic guanosine-3',-5'-monophasphate (cGMP) signaling pathways underlying vascular smooth muscle cell relaxation, albeit many questions relating to how nitrates work at the cellular level remain unanswered. Physiologically, the anti-angina effects of nitrates are mostly due to peripheral venous dilatation leading to reduction in preload and therefore left ventricular wall stress, and, to a lesser extent, epicardial coronary artery dilatation and lowering of systemic blood pressure. By counteracting ischemic mechanisms, short-acting nitrates offer rapid relief following an angina attack. Long-acting nitrates, used commonly for angina prophylaxis are recommended second-line, after beta-blockers and calcium channel antagonists. Nicorandil is a balanced vasodilator that acts as both NO donor and arterial K(+) ATP channel opener. Nicorandil might also exhibit cardioprotective properties via mitochondrial ischemic preconditioning. While nitrates and nicorandil are effective pharmacological agents for prevention of angina symptoms, when prescribing these drugs it is important to consider that unwanted and poorly tolerated hemodynamic side-effects such as headache and orthostatic hypotension can often occur owing to systemic vasodilatation. It is also necessary to ensure that a dosing regime is followed that avoids nitrate tolerance, which not only results in loss of drug efficacy, but might also cause endothelial dysfunction and increase long-term cardiovascular risk. Here we provide an update on the pharmacological management of chronic stable angina using nitrates and nicorandil.

Study of the possible medical and medication explanatory factors of angiographic outcomes in patients with acute ST elevation myocardial infarction undergoing primary percutaneous intervention

Background:

Myocardial blush grade (MBG), thrombolysis in myocardial infarction (TIMI) and corrected TIMI frame count (cTFC) are indices of successful angiographic reperfusion. This study sought to determine the predictors of angiographically successful reperfusion including demographic, clinical and angiographic factors in patients with ST elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI).

Materials and Methods:

A cross-sectional study of patients with a confirmed diagnosis of STEMI undergoing pPCI was designed. Eligible patients referring to a university heart center were enrolled in the study from March 2012 to December 2012. Successful epicardial reperfusion was defned as TIMI flow grade 3 or cTFC<= 28 frames and successful myocardial reperfusion as MBG 2 or 3.

Results:

The study population consisted of 100 patients, including 74 males and 26 females, with mean ± standard deviation age of 58.27 ± 11.60 years. Achieving open microvasculature (MBG 2/3) was positively associated with a history of nitrate intake (P = 0.03) and history of calcium channel blocker (CCB) intake (P = 0.005). Hyperglycemia was inversely associated with achieving a final cTFC ≤ 28 frames (r = −0.32, P = 0.001).

Conclusions:

Our findings suggest that patients with a history of nitrate and CCB intake had a higher likelihood of successful PCI. In addition, patients with a higher blood glucose level on admission may have a reduced rate of reperfusion success. Future studies with a larger sample size are recommended to investigate the significant relationships observed in this study.

Coronary risk assessment and management options in chronic kidney disease patients prior to kidney transplantation

Cardiovascular disease remains the most important cause of morbidity and mortality among kidney transplant recipients. Nearly half the deaths in transplanted patients are attributed to cardiac causes and almost 5% of these deaths occur within the first year after transplantation. The ideal strategies to screen for coronary artery disease (CAD) in chronic kidney disease patients who are evaluated for kidney transplantation (KT) remain controversial. The American Society of Transplantation recommends that patients with diabetes, prior history of ischemic heart disease or an abnormal ECG, or age ≥50 years should be considered as high-risk for CAD and referred for a cardiac stress test and only those with a positive stress test, for coronary angiography. Despite these recommendations, vast variations exist in the way these patients are screened for CAD at different transplant centers. The sensitivity and specificity of noninvasive cardiac tests in CKD patients is much lower than that in the general population. This has prompted the use of direct diagnostic cardiac catheterization in high-risk patients in several transplant centers despite the risks associated with this invasive procedure. No large randomized controlled trials exist to date that address these issues. In this article, we review the existing literature with regards to the available data on cardiovascular risk screening and management options in CKD patients presenting for kidney transplantation and outline a strategy for approach to these patients.

To what degree is amelioration of angina following coronary revascularization associated with improvement in myocardial perfusion?

OBJECTIVE

To examine the association between changes in chest pain and changes in perfusion following revascularization as assessed by clinical evaluation and myocardial perfusion imaging (MPI) in patients with stable angina.

DESIGN

In a prospective series of 380 patients (58.8 +/- 8.8 years) referred to angiography because of known or suspected stable angina, changes in chest discomfort and changes in perfusion after 2 years were assessed in 144 patients, who underwent revascularization, and 236, who did not. The decision to treat invasively was made without knowledge of the result of MPI.

RESULTS

In revascularized patients, the presence of typical/atypical angina was reduced from 93% to 36% and the improvement was associated with improvement in perfusion. A small improvement in perfusion induced a high frequency of change from angina to no pain, whereas a further reduction caused little extra change. In non-revascularized patients the change in chest discomfort was not related to changes in perfusion, which were rarely present.

CONCLUSION

Alleviation of chest discomfort 2 years after revascularization is associated with improvements in perfusion. This association appeared to be an all-or-nothing phenomenon. Non-revascularized patients also exhibited improvements in chest discomfort despite insignificant changes in perfusion.

Functional capacity and cardiovascular assessment: submaximal exercise testing and hidden candidates for pharmacologic stress

Submaximal exercise testing is often used to estimate functional capacity in non-athletes, to assess cardiovascular disease in elderly or frail patients, to demonstrate exercise equipment, or to risk-stratify patients after myocardial infarction. However, submaximal exercise testing is not sufficiently sensitive, specific, or predictive to have widespread clinical utility, except in post-myocardial infarction protocols. Many patients for whom submaximal exercise testing is not useful are unable to exercise sufficiently for maximal testing and are referred for imaging with pharmacologic stress. Although some patients who are unable to exercise adequately are easily recognized, many are not. The identification of such patients before they fail a maximal exercise test attempt is beneficial to both the patient and the imaging laboratory.

Sequential single-photon emission computed tomography myocardial perfusion imaging

The utility of stress myocardial perfusion imaging (MPI) for the diagnosis and prognosis of coronary artery disease (CAD) has been firmly established in numerous clinical studies and has become an essential component of clinical practice. Stress MPI is now used regularly to guide initial risk stratification and management of patients with CAD. Because stress MPI provides an assessment of the physiologic significance of CAD, it is a particularly attractive procedure for assessing follow-up risk. Today, sequential stress MPI is being used increasingly to track disease progression, assess follow-up risk, detect restenosis following revascularization, and evaluate the efficacy of aggressive medical therapy and risk-factor modification. By providing serial snapshots of the disease and its impact on perfusion, sequential stress MPI may alter treatment decisions and ultimately improve long-term patient management and outcomes. Use of sequential stress MPI to detect changes in perfusion following surgical or medical therapies is being tested currently in the Clinical Outcomes Using Revascularization and Aggressive Drug Evaluation (COURAGE) and Adenosine Sestamibi Single-Photon Emission Computed Tomography Postinfarction Evaluation (INSPIRE) trials.

Irbesartan has a masking effect on dipyridamole stress induced myocardial perfusion defects

BACKGROUND AND AIM

The angiotensin II type 1 (AT1) receptor antagonist irbesartan is used for the treatment of hypertension, but its anti-ischaemic effect is not yet known. Our aim was to assess the effect of irbesartan administration on the diagnostic yield of 99mTc sestamibi single photon emission computed tomography (SPECT) in patients with coronary artery disease (CAD) after dipyridamole stress.

METHODS

Our study group consisted of 13 patients (11 men and two women; mean age, 53.3 +/- 10.6 years; body mass index, 26.9 +/- 3.3 kg x m(-2)) with angiographically documented CAD. All patients underwent SmTc sestamibi SPECT studies at rest, before (STRESS-1) and 2 weeks after irbesartan (150 mg daily) administration (STRESS-2) at dipyridamole stress. The extent and severity of defects were analysed by using visual and quantitative 99mTc sestamibi SPECT.

RESULTS

The mean summed stress score was significantly higher during the STRESS-1 study than the STRESS-2 study (13.2 +/- 7.4 vs. 11 +/- 7.4, P=0.003). The mean size of perfusion defects at stress was significantly larger for the STRESS-1 group than the STRESS-2 group (17.8% +/- 2.85% vs. 15.3% +/- 2.95%, P=0.01).

CONCLUSION

Our study showed that the AT1 receptor blocker irbesartan reduces the extent and severity of 99mTc sestamibi perfusion defects after dipyridamole stress in patients with CAD. Irbesartan may alter coronary blood flow reserve. The continued use of irbesartan before stress myocardial perfusion SPECT has a masking effect on stress induced myocardial perfusion defects. For this reason AT1 receptor blockers must be stopped before stress myocardial perfusion scintigraphic examinations.