Prediction of outcome of patients with life-threatening ventricular arrhythmias treated with automatic implantable cardioverter-defibrillators using SPECT perfusion imaging

Evaluation of Need for Implantable Cardioverter-Defibrillator by Thallium-201 Scintigraphy Among Japanese Patients With Prior Myocardial Infarction

BACKGROUND

Identifying who among current Japanese patients with prior myocardial infarction (MI) would benefit from an implantable cardioverter-defibrillator (ICD) is imperative. Accordingly, this study seeks to determine whether single-photon emission computed tomography (SPECT) can help identify such patients. Methods and Results: This retrospective study enrolled 60 consecutive patients with prior MI who underwent stress thallium-201 SPECT and ICD implantation from February 2000 to October 2014. Occurrence of arrhythmic death and/or or appropriate ICD therapy, defined as shock or antitachycardia pacing for ventricular fibrillation or tachycardia, was identified until November 2016. During the median follow-up interval of 6.6 years, 18 (30%) patients experienced arrhythmic death and/or appropriate ICD therapy. Multivariate Cox proportional hazard regression analysis revealed that the summed stress score (SSS) [hazard ratio (HR)=1.14; P=0.005] and left ventricular ejection fraction (LVEF) at rest (HR=0.92; P=0.038) were significantly associated with the occurrence of arrhythmic events. Patients with SSS ≥21 and LVEF ≤30%, which were determined to be the best cutoff points, had significantly higher incidence of the arrhythmic events than the other patients (64% vs. 11%; HR=7.18; log-rank P=0.001).

CONCLUSIONS

SSS using stress thallium-201 SPECT in combination with LVEF can help determine the need for ICD therapy among current Japanese patients with prior MI.

Long-term prognostic value of inducible and resting perfusion defects detected by single-photon emission computed tomography in the era of wide availability of coronary revascularization

PURPOSE

To assess the long-term prognostic value of various types of perfusion defects detected by single-photon emission computed tomography (SPECT) in patients with stable angina.

METHODS

Seven hundred and thirty two patients (299 men, mean age 57 ± 9 years) with suspected or known stable coronary artery disease underwent rest/exercise SPECT protocol using 99mTc-methoxyisobutylisonitrile (MIBI). All patients completed clinical follow-up regarding cardiac events (cardiac death, sudden cardiac death, acute coronary syndrome, revascularization, cardiac hospitalization) for a mean period of 58 ± 8 months. Event rates were analysed in subgroups defined according to the presence of fixed or inducible myocardial perfusion defects.

RESULTS

During the follow-up, 15 cardiac deaths were recorded, 13 of which were qualified as a sudden cardiac death, 59 acute coronary syndromes, 65 revascularizations and 209 cardiac hospitalizations. The presence of inducible perfusion defects on SPECT was associated with a high risk for occurrence of all analysed end points: sudden cardiac death (HR = 3·96, P = 0·01), cardiac hospitalization (HR = 1·5, P = 0·004), coronary syndrome (HR = 2·33, P = 0·001) and coronary revascularization (HR = 2·76, P = 0·0002), except for the cardiac death (P = 0·27). Resting perfusion defects were highly predictive for cardiac death (HR = 7·45; P = 0·001), but not for other cardiac events (P = NS). The presence of any (inducible or resting) perfusion defects was associated with a high risk of all cardiovascular complications.

CONCLUSIONS

In long-term follow-up, SPECT proved highly predictive of cardiac events in patients with suspected or known CAD. In the revascularization era, cardiac death is most accurately related to the presence of resting perfusion defects, but all other cardiac events were better predicted by inducible perfusion defects.

MRI for the assessment of myocardial viability

Accurate distinction between viable and infarcted myocardium is important for assessment of patients who have cardiac dysfunction. Through the technique of delayed-enhancement MRI (DE-MRI), viable and infarcted myocardium can be simultaneously identified in a manner that closely correlates with histopathology findings. This article provides an overview of experimental data establishing the physiologic basis of DE-MRI-evidenced hyperenhancement as a tissue-specific marker of myocardial infarction. Clinical data concerning the utility of transmural extent of hyperenhancement for predicting response to medical and revascularization therapy are reviewed. Studies directly comparing DE-MRI to other viability imaging techniques are presented, and emerging applications for DE-MRI are discussed.

MRI for the Assessment of Myocardial Viability

Accurate distinction between viable and infarcted myocardium is important for assessment of patients who have cardiac dysfunction. Through the technique of delayed-enhancement MRI (DE-MRI), viable and infarcted myocardium can be simultaneously identified in a manner that closely correlates with histopathology findings. This article provides an overview of experimental data establishing the physiologic basis of DE-MRI-evidenced hyperenhancement as a tissue-specific marker of myocardial infarction. Clinical data concerning the utility of transmural extent of hyperenhancement for predicting response to medical and revascularization therapy are reviewed. Studies directly comparing DE-MRI to other viability imaging techniques are presented, and emerging applications for DE-MRI are discussed.

Prognostic importance of wall motion abnormalities in patients with ischemic cardiomyopathy and an implantable cardioverter-defibrillator

Patients with extensive regional wall motion abnormalities are predisposed to development of ventricular tachyarrhythmia. The prognostic effect of this in patients with an implantable cardioverter-defibrillator (ICD) and coronary artery disease (CAD) is not known. Echocardiographic left ventricular systolic indexes, wall motion score index (WMSI), and extent of regional akinesia in 140 patients (65 +/- 10 years old; 92% men) with an ICD and CAD were studied. Arrhythmic events requiring ICD therapy and causing death (n = 41, 29%) were recorded over a mean follow-up of 1.4 +/- 0.8 years. Left ventricular basal fractional shortening, ejection fraction, global WMSI, and extent of akinesia, especially in the inferoposterior regions of a right coronary artery territory, were univariate predictors (all p values <0.05). Global WMSI (hazard ratio 2.18, 95% confidence interval 1.03 to 4.65, p = 0.04) and fractional shortening (hazard ratio 0.93, 95% confidence interval 0.88 to 1.00, p = 0.04) were multivariate predictors. Global WMSI (p = 0.04) and > or =2 right coronary region akinetic segments (p = 0.05) provided incremental risk prediction to left ventricular ejection fraction in a global risk-assessment model (chi-square p = 0.001). Presence of right coronary region akinesia better identified those at increased risk of events (p = 0.02) compared with the presence of left anterior descending region akinesia (p = 0.2), independent of systolic function. In conclusion, global WMSI and left ventricular basal fractional shortening were important additional risk predictors of ICD events in CAD. Global WMSI and right coronary region inferoposterior akinesia provided independent and incremental risk assessment to left ventricular ejection fraction and improved identification of those at increased risk of ICD-related events in patients with ischemic cardiomyopathy.

Association of Myocardial Ischemia With Mortality and Implantable Cardioverter-Defibrillator Therapy in Patients With Coronary Artery Disease at Risk of Arrhythmic Death

OBJECTIVES

We sought to assess the relation between myocardial ischemia during stress echocardiography and major events in patients with implantable cardioverter-defibrillator (ICD).

BACKGROUND

The association of myocardial ischemia with subsequent ICD therapy and mortality is unknown.

METHODS

We studied 90 patients (age 65 +/- 13 years, 27 women) with history of coronary heart disease who received ICD for primary (53 patients) or secondary (37 patients) prevention of sudden cardiac death. Sixty-five (72%) patients had a previous coronary artery bypass surgery. Patients underwent exercise treadmill or dobutamine stress echocardiography. Ischemia was defined as new or worsening wall motion abnormalities. End points were death and appropriate ICD therapy.

RESULTS

Mean ejection fraction was 34 +/- 12%. During a mean follow-up of 2.8 +/- 1.5 years, 5 patients died and 19 patients had ICD therapy. Ischemia was detected in 20 of 24 patients with subsequent events and in 24 of 66 patients without (83% vs. 36%, p < 0.001). Events occurred in 17 of the 32 patients (53%) with both ischemia and inducible ventricular tachycardia (VT) on electrophysiologic (EP) studies. None of the 16 patients without ischemia or inducible VT on EP studies had events. In a Cox multivariate analysis model, independent predictors of events were a history of spontaneous sustained VT (hazard ratio [HR] 1.9, 95% confidence interval [CI] 1.3 to 3.8), inducible VT on EP studies (HR 1.7, 95% CI 1.2 to 4.5), and ischemia (HR 2.1, 95% CI 1.2 to 3.5).

CONCLUSIONS

Ischemia during stress echocardiography is an independent predictor of death and ICD therapy in patients with coronary heart disease at high risk of arrhythmic death. Patients without inducible ischemia or VT on a previous EP study have a very low risk of events. A combination of ischemia and a positive EP study is associated with a very high risk of events.

Prognostic validation of a 17-segment score derived from a 20-segment score for myocardial perfusion SPECT interpretation

BACKGROUND

Recently, a 17-segment model of the left ventricle has been recommended as an optimally weighted approach for interpreting myocardial perfusion single photon emission computed tomography (SPECT). Methods to convert databases from previous 20- to new 17-segment data and criteria for abnormality for the 17-segment scores are needed.

METHODS AND RESULTS

Initially, for derivation of the conversion algorithm, 65 patients were studied (algorithm population) (pilot group, n = 28; validation group, n = 37). Three conversion algorithms were derived: algorithm 1, which used mid, distal, and apical scores; algorithm 2, which used distal and apical scores alone; and algorithm 3, which used maximal scores of the distal septal, lateral, and apical segments in the 20-segment model for 3 corresponding segments of the 17-segment model. The prognosis population comprised 16,020 consecutive patients (mean age, 65 +/- 12 years; 41% women) who had exercise or vasodilator stress technetium 99m sestamibi myocardial perfusion SPECT and were followed up for 2.1 +/- 0.8 years. In this population, 17-segment scores were derived from 20-segment scores by use of algorithm 2, which demonstrated the best agreement with expert 17-segment reading in the algorithm population. The prognostic value of the 20- and 17-segment scores was compared by converting the respective summed scores into percent myocardium abnormal. Conversion algorithm 2 was found to be highly concordant with expert visual analysis by the 17-segment model (r = 0.982; kappa = 0.866) in the algorithm population. In the prognosis population, 456 cardiac deaths occurred during follow-up. When the conversion algorithm was applied, extent and severity of perfusion defects were nearly identical by 20- and derived 17-segment scores. The receiver operating characteristic curve areas by 20- and 17-segment perfusion scores were identical for predicting cardiac death (both 0.77 +/- 0.02, P = not significant). The optimal prognostic cutoff value for either 20- or derived 17-segment models was confirmed to be 5% myocardium abnormal, corresponding to a summed stress score greater than 3. Of note, the 17-segment model demonstrated a trend toward fewer mildly abnormal scans and more normal and severely abnormal scans.

CONCLUSION

An algorithm for conversion of 20-segment perfusion scores to 17-segment scores has been developed that is highly concordant with expert visual analysis by the 17-segment model and provides nearly identical prognostic information. This conversion model may provide a mechanism for comparison of studies analyzed by the 17-segment system with previous studies analyzed by the 20-segment approach.

Utility of stress myocardial perfusion imaging performed before electrophysiologic testing

BACKGROUND

Patients considered for electrophysiologic study (EPS) are often first referred for stress myocardial perfusion scintigraphy (MPS) to assess for inducible ischemia before testing. The purpose of this investigation was to determine the utility of this approach by examining the relationship between MPS and any interim cardiac catheterization and revascularization, as well as the results and safety of EPS.

METHODS AND RESULTS

All patients undergoing EPS within 30 days after MPS at our institution between January 1997 and June 2000 were studied. Two hundred fifty-one patients met the inclusion criteria. The incidence of inducible sustained monomorphic ventricular tachycardia at EPS (IND) was 16%. One hundred twenty-nine patients had MPS ischemia (83 with high-risk features), but only twelve patients in all underwent revascularization between MPS and EPS. There were no ischemic complications during EPS. The presence of isolated ischemia on MPS was associated with a low rate of IND, not different from normal MPS findings (2%-3%). The combination of infarct and ischemia on MPS was associated with a high rate of IND that was similar to infarct alone (34% and 50%, respectively; P =.28).

CONCLUSIONS

Patients with high-risk MPS results are more likely to undergo revascularization before EPS than patients with low-risk or normal MPS results. However, most patients with high-risk MPS results undergo EPS without interim revascularization, and no patient had an ischemia-related complication at EPS. Larger studies will be required to confirm this observation. MPS infarct, not ischemia, is associated with IND at EPS.

Prevention of sudden death in patients with coronary artery disease: do lipid-lowering drugs play a role?

Ventricular arrhythmias are the most common cause of sudden cardiac death in patients with coronary artery disease. Since treatment of hypercholesterolemia in patients with coronary artery disease reduces the risk of major coronary events by about 30%, one could speculate that this treatment could also result in a reduction of arrhythmic episodes in high-risk patients. In this review, the importance of myocardial ischemia as a trigger for ventricular arrhythmias, as well as the available data that suggest a possible effect of anti-ischemic treatments, including lipid-lowering drugs, on these arrhythmias are presented. Also, possible mechanisms and future research to test the hypothesis that lipid-lowering drugs can reduce life-threatening ventricular arrhythmias are discussed.

QT dispersion is not related to infarct size or inducibility in patients with coronary artery disease and life threatening ventricular arrhythmias

OBJECTIVE

To relate QT parameters to infarct size and inducibility during electrophysiological studies.

DESIGN

Analysis of a prospective register.

SETTING

University hospital.

PATIENTS

64 patients with coronary artery disease and documented life threatening ventricular arrhythmias.

INTERVENTIONS

Measurements of QT-max, QTc-max, and QT dispersion (QT-d) on a simultaneous 12 lead ECG (50 mm/s). Estimation of myocardial infarct size with radionuclide left ventricular ejection fraction (LVEF), echocardiography (left ventricular end diastolic diameter, LVEDD), and a defect score based on a quantitative stress redistribution 201-thallium perfusion study. Electrophysiological study to assess inducibility.

RESULTS

Mean (SD) QT parameters were: QT-max 440 (50) ms, QTc-max 475 (46) ms, and QT-d 47 (20) ms. Mean (SD) estimates of infarct size were: LVEF 34 (13)%, LVEDD 61 (9) mm, and defect score 18 (11). There was no significant correlation between any index of infarct size and QT parameters. QT parameters were not significantly different between patients with inducible (n = 57) and non-inducible arrhythmias (n = 7) (QT-max: 416 (30) v 443 (51) ms, p = 0.18; QTc-max 485 (34) v 473 (47) ms, p = 0.34; QT-d 47 (12) v 47 (21) ms, p = 0.73). Non-inducible patients had a significant lower defect score: 8 (9) v 19 (11), p = 0.02, but comparable LVEF: 38 (12)% v 34 (12)%, p = 0.58, and LVEDD: 54 (10) v 61 (8) mm, p = 0.13.

CONCLUSIONS

QT parameters are not influenced by infarct size and do not predict inducibility during electrophysiological study in patients with coronary artery disease and malignant ventricular arrhythmias. In contrast, the amount of scar tissue determined by perfusion imaging is strongly correlated with inducibility.

Prognostic utility of myocardial viability assessment

Myocardial viability assessment is useful in patients with severe coronary artery disease and severe left ventricular dysfunction. Whereas most studies have focused on recovery of regional function, there are emerging data on patient outcome. Review of these data suggests that patients with chronic ischemia, cardiomyopathy, and viable myocardium who are treated medically have a worse, outcome than those treated with coronary revascularization. However, there are no prospective randomized trials. We present perspectives for future studies.

Hemodynamic effects of arbutamine

This study examined the hemodynamic effects of arbutamine, a synthetic catecholamine, in 12 patients with and 7 patients without coronary artery disease. Arbutamine produced a balanced positive inotropic (increase in left ventricular dp/dt) and chronotropic effect (increase in heart rate).

Utility of stress single-photon emission computed tomography (SPECT) perfusion imaging in predicting outcome after coronary artery bypass grafting

Previous studies have examined the predictors of outcome in medically treated patients with coronary artery disease (CAD). There is limited information on predictors of outcome after coronary artery bypass grafting (CABG). This study examined the predictors of outcome of 255 patients with CAD, at a mean time of 5 years after CABG for angina pectoris. The 255 patients underwent coronary angiography and stress single-photon emission computed tomography (SPECT) myocardial perfusion imaging after CABG. During a mean follow-up of 41 +/- 28 months after stress testing, there were 34 hard events (24 cardiac deaths and 10 nonfatal myocardial infarctions). The hemodynamics during stress testing, and age and gender were not predictors of events. The SPECT variables of multivessel perfusion abnormality, perfusion deficit size, and increased lung thallium uptake were predictors of death and total events by uni- and multivariate survival analysis. There were 14 events in 45 patients (31%) with multivessel abnormality and increased lung thallium uptake, 14 events in 101 patients (14%) with either multivessel abnormality or increased lung uptake, and 6 events in 109 patients (6%) with neither of these 2 variables (p = 0.0001). The annual mortality and total event rates were 7.5% and 9.5% with both variables, 3.4% and 4.3% with either variable, and 0.6% and 1.7% with neither of the variables (p = 0.01). Thus, stress SPECT perfusion imaging is useful to stratify patients after CABG into low, intermediate, and high risk groups for future cardiac events.