Reciprocal ST-segment depression associated with exercise-induced ST-segment elevation indicates residual viability after myocardial infarction

Myocardial Viability Testing in the Management of Ischemic Heart Failure

Although major advances have occurred lately in medical therapy, ischemic heart failure remains an important cause of death and disability. Viable myocardium represents a cause of reversible ischemic left ventricular dysfunction. Coronary revascularization may improve left ventricular function and prognosis in patients with viable myocardium. Although patients with impaired left ventricular function and multi-vessel coronary artery disease benefit the most from revascularization, they are at high risk of complications related to revascularization procedure. An important element in selecting the patients for myocardial revascularization is the presence of the viable myocardium. Multiple imaging modalities can assess myocardial viability and predict functional improvement after revascularization, with dobutamine stress echocardiography, nuclear imaging tests and magnetic resonance imaging being the most frequently used. However, the role of myocardial viability testing in the management of patients with ischemic heart failure is still controversial due to the failure of randomized controlled trials of revascularization to reveal clear benefits of viability testing. This review summarizes the current knowledge regarding the concept of viable myocardium, depicts the role and tools for viability testing, discusses the research involving this topic and the controversies related to the utility of myocardial viability testing and provides a patient-centered approach for clinical practice.

Clinical Significance of Reciprocal ST-segment Changes in Patients With STEMI: A Cardiac Magnetic Resonance Imaging Study

INTRODUCTION AND OBJECTIVES

We sought to determine the association of reciprocal change in the ST-segment with myocardial injury assessed by cardiac magnetic resonance (CMR) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

METHODS

We performed CMR imaging in 244 patients who underwent primary PCI for their first STEMI; CMR was performed a median 3 days after primary PCI. The first electrocardiogram was analyzed, and patients were stratified according to the presence of reciprocal change. The primary outcome was infarct size measured by CMR. Secondary outcomes were area at risk and myocardial salvage index.

RESULTS

Patients with reciprocal change (n=133, 54.5%) had a lower incidence of anterior infarction (27.8% vs 71.2%, P < .001) and shorter symptom onset to balloon time (221.5±169.8 vs 289.7±337.3min, P=.042). Using a multiple linear regression model, we found that patients with reciprocal change had a larger area at risk (P=.002) and a greater myocardial salvage index (P=.04) than patients without reciprocal change. Consequently, myocardial infarct size was not significantly different between the 2 groups (P=.14). The rate of major adverse cardiovascular events, including all-cause death, myocardial infarction, and repeat coronary revascularization, was similar between the 2 groups after 2 years of follow-up (P=.92).

CONCLUSIONS

Reciprocal ST-segment change was associated with larger extent of ischemic myocardium at risk and more myocardial salvage but not with final infarct size or adverse clinical outcomes in STEMI patients undergoing primary PCI.

Myocardial Viability: From Proof of Concept to Clinical Practice

Ischaemic left ventricular (LV) dysfunction can arise from myocardial stunning, hibernation, or necrosis. Imaging modalities have become front-line methods in the assessment of viable myocardial tissue, with the aim to stratify patients into optimal treatment pathways. Initial studies, although favorable, lacked sufficient power and sample size to provide conclusive outcomes of viability assessment. Recent trials, including the STICH and HEART studies, have failed to confer prognostic benefits of revascularisation therapy over standard medical management in ischaemic cardiomyopathy. In lieu of these recent findings, assessment of myocardial viability therefore should not be the sole factor for therapy choice. Optimization of medical therapy is paramount, and physicians should feel comfortable in deferring coronary revascularisation in patients with coronary artery disease with reduced LV systolic function. Newer trials are currently underway and will hopefully provide a more complete understanding of the pathos and management of ischaemic cardiomyopathy.

Myocardial viability: what we knew and what is new

Some patients with chronic ischemic left ventricular dysfunction have shown significant improvements of contractility with favorable long-term prognosis after revascularization. Several imaging techniques are available for the assessment of viable myocardium, based on the detection of preserved perfusion, preserved glucose metabolism, intact cell membrane and mitochondria, and presence of contractile reserve. Nuclear cardiology techniques, dobutamine echocardiography and positron emission tomography are used to assess myocardial viability. In recent years, new advances have improved methods of detecting myocardial viability. This paper summarizes the pathophysiology, methods, and impact of detection of myocardial viability, concentrating on recent advances in such methods. We reviewed the literature using search engines MIDLINE, SCOUPS, and EMBASE from 1988 to February 2012. We used key words: myocardial viability, hibernation, stunning, and ischemic cardiomyopathy. Recent studies showed that the presence of viable myocardium was associated with a greater likelihood of survival in patients with coronary artery disease and LV dysfunction, but the assessment of myocardial viability did not identify patients with survival benefit from revascularization, as compared with medical therapy alone. This topic is still debatable and needs more evidence.

Detection of multivessel disease post myocardial infarction using an exercise-induced QRS score

OBJECTIVE

The aim of this study was to investigate the ability of Athens QRS score values to detect stenoses in other coronary arteries than the obstructed ones (which caused the myocardial infarction [MI]) in patients with a history of MI.

METHODS

We studied 125 patients (93 males and 32 females, mean age 54 +/- 7 years [range 45-68 years]) with a history of MI (46 patients with anterior MI, 54 patients with inferior MI, 25 patients with lateral MI). All patients underwent treadmill exercise testing and coronary arteriography.

RESULTS

Athens QRS score values were inversely related to the extent of CAD: -0.5 +/- 0.3 mm for patients with 1-VD (obstructed vessel), -3.4 +/- 2.2 mm for patients with 2-VD (obstructed vessel and stenosis in another vessel), and -5 +/- 1.8 mm for patients with 3-VD (obstructed vessel and stenoses in two more vessels). The ROC curves for the detection of multivessel disease showed that the area under the curve for QRS score values < -3 mm is significantly higher than the curve for ST-segment depression > or = 1 mm (0.948 vs 0.792, P < 0.001).

CONCLUSIONS

Values of the Athens QRS score less than -3 may distinguish single- from multivessel coronary artery disease in patients with a history of MI.

Exercise-induced prolongation of the infarct-related Q-waves as a marker of myocardial viability in the infarcted area

OBJECTIVE

It is known that exercise-induced ischemia in patients with coronary artery disease (CAD) may produce QRS prolongation in the surface electrocardiogram (ECG). To investigate the presence of exercise-induced Q-wave prolongation in patients with single-vessel CAD and Q-wave myocardial infarction (MI), in association with the presence of reversible perfusion defects during thallium scintigraphy in the infarcted area.

METHODS

107 consecutive patients (89 males, mean age 56+/-8 years) were evaluated. All patients underwent coronary arteriography, maximal treadmill exercise testing and thallium-201 scintigraphy. Q-wave duration was measured both before exercise testing and during maximal heart rate from 12-lead ECGs recorded with a paper speed of 50 mm/s.

RESULTS

Only 57 out of the 107 studied patients showed reversible perfusion defects in the infarcted area during thallium scintigraphy. Q-wave duration was significantly increased from the resting to the stress ECG (DeltaQ-wave duration) in patients with reversible perfusion defects in the infarcted areas (10+/-13 ms), but not in patients with fixed defects in the infarcted zone (-2.0+/-5 ms, p<0.01). The sensitivities and the specificities of Q-wave prolongation, ST segment elevation, and the combination of ST segment elevation with ST segment depression in the reciprocal leads for the detection of myocardial viability in the infarcted area were 82%, 48%, 29% and 88%, 50%, and 90%, respectively.

CONCLUSIONS

Exercise-induced Q-wave prolongation is demonstrated in those patients with single-vessel CAD and a recent MI who show reversible perfusion defects in thallium scintigraphy. Exercise-induced Q-wave prolongation was found to be a sensitive and specific ECG marker for the detection of myocardial viability in the infarcted area.

Reversible defect of 123I-15-(p-iodophenyl)-9-(R,S)-methylpentadecanoic acid indicates residual viability within infarct-related area

To evaluate the relationship between the reversible defect of 123I-15-(p-iodophenyl)-9-(R,S)-methylpentadecanoic acid (9MPA) and residual viability within an infarct-related area, we performed resting single photon emission computed tomography (SPECT) with 9MPA and positron emission tomography (PET) with 18F-deoxyglucose (FDG) and 13N-ammonia (NH3) in 7 patients with prior myocardial infarction. 9MPA-SPECT was obtained 2 min (early) and 50 min (delayed) after tracer injection. Tomographic images of the left ventricle were divided into 13 segments to correlate the regional uptake of each tracer. Residual viability within an infarct-related segment was confirmed by NH3- and FDG-PET. Twenty-six infarct-related segments, confirmed by NH3-PET, showed reduced uptake of 9MPA on early images. In these 26 segments, 6 showed reversible defect of 9MPA and 20 showed fixed defect on delayed images. Residual viability was present in all segments exhibiting reversible 9MPA defect and 7 segments (35%) exhibiting fixed defect (p < 0.05). The sensitivity, specificity and accuracy of reversible 9MPA defect for the detection of myocardial viability were 46%, 100%, and 73%, respectively. Myocardial clearance of 9MPA was significantly slower in non-viable segments than in ischemic but viable segments (4.9+/-5.1% vs. 10.1+/-5.3%; p < 0.05). These data suggest that a reversible 9MPA defect indicates residual viability within the infarct-related area.

Copper-62 ATSM as a hypoxic tissue tracer in myocardial ischemia

Copper-62 labeled diacetyl-bis(N4-methylthiosemicarbazone) (62Cu-ATSM) has been proposed as a generator produced positron-emitting tracer for hypoxic tissue imaging. To clarify the usefulness of 62Cu-ATSM for myocardial ischemia, 62Cu-ATSM PET was performed in 7 patients with coronary artery disease. Increased myocardial uptake of 62Cu-ATSM was observed (myocardium/blood ratio: 3.09) in one patient with unstable angina, who had increased 18F-fluorodeoxyglucose (18F-FDG) uptake under the fasting condition. The other 6 patients, who were clinically stable, did not have increased 62Cu-ATSM uptake, although abnormal 18F-FDG uptake was seen in 4 patients. This preliminary study suggests that 62Cu-ATSM is a promising PET tracer for hypoxic imaging in acute ischemia.

Clinical significance of reverse redistribution on resting thallium-201 imaging in patients with vasospastic angina

To evaluate the clinical significance of reverse redistribution (RR) of resting 201Tl single photon emission computed tomography (SPECT) in patients with vasospastic angina (VSA), we performed left ventriculography, coronary angiography and resting 201Tl-SPECT in 22 patients with VSA. Left ventriculography showed abnormal wall motion in 17 of 22 patients (77%) and 37 of 154 segments. Thirty-one of these 37 segments (84%) were within the area perfused by coronary arteries showing acetylcholine-induced vasospasm. On 201Tl images, abnormal findings were observed in 11 of 22 patients (50%), and among them, 7 patients (32%) had RR. Seven of 37 segments (19%) having abnormal regional wall motion had RR of 201TI, and in 6 of these 7 segments (86%), accumulation of 123I-BMIPP was found to be reduced. We conclude that repetitive brief myocardial ischemia may cause myocardial injuries in patients with VSA, and that the presence of RR of 201Tl indicates the presence of myocardial injury in these patients.

Comparison of myocardial blood flow during dobutamine-atropine infusion with that after dipyridamole administration in normal men

OBJECTIVES

The present study was designed to compare the absolute myocardial blood flow (MBF) after intravenous dipyridamole infusion with that during dobutamine-atropine administration in normal healthy male volunteers.

BACKGROUND

Both safety and usefulness of dobutamine-atropine stress in myocardial perfusion imaging have been reported. However, no information exists on whether the magnitude ofhyperemia achieved with dipyridamole and dobutamine-atropine is comparable.

METHODS

Myocardial blood flow was measured with positron emission tomography and 15O-labeled water in 20 healthy young men (23 +/- 3 years) 1) at baseline, 2) after dipyridamole infusion (0.56 mg/kg over 4 min), and 3) during dobutamine (40 microg/kg/min) and atropine (0.25 to 1.0 mg) infusion.

RESULTS

The MBF was significantly increased during dipyridamole infusion and during dobutamine-atropine stress compared with at rest (4.33 +/- 1.23 and 5.89 +/- 1.58 vs. 0.67 +/- 0.16 ml/min/g, respectively, p < 0.0001). Moreover, dobutamine-atropine infusion produced greater MBF compared with dipyridamole (p = 0.0011), while coronary vascular resistance did not differ significantly after dipyridamole administration and during dobutamine-atropine infusion (17.6 +/- 7.9 vs. 18.6 +/- 5.6 mm Hg/[ml/min/g], respectively).

CONCLUSIONS

Near maximal coronary vasodilatation caused by dipyridamole is attainable using dobutamine and atropine in young healthy volunteers. Dobutamine in conjunction with atropine is no less effective than dipyridamole in producing myocardial hyperemia.