Impact of myocardial viability and left ventricular lead location on clinical outcome in cardiac resynchronization therapy recipients with ischemic cardiomyopathy.

INTRODUCTION: Cardiac resynchronization therapy (CRT) recipients with ischemic cardiomyopathy (ICM) have scar segments that may limit ventricular resynchronization and clinical response. The impact of myocardial viability at the left ventricular (LV) pacing site on CRT response is poorly elucidated. METHODS AND RESULTS: A retrospective cohort of 160 ICM patients with single photon emission computed tomography-myocardial perfusion imaging before device implantation were included. Coronary venous angiography and chest radiographs helped classify segmental location of LV lead (LVL). The primary outcome was a composite of heart failure (HF) hospitalization and mortality at 3 years, and secondary outcome was change in systolic function at 6 months. The patients were divided into groups based on the myocardial substrate at the site of LVL: LVL on or adjacent to (1) normal myocardium (LVL-N, n = 64), (2) segmental scar (LVL-S, n = 62), and (3) scar and ischemia (LVL-SI, n = 34). Upon follow-up, 75 (47%) patients reached primary endpoint with a higher incidence noted in LVL-S (60%), and LVL-SI (53%), compared to 31% in LVL-N (P = 0.004). Kaplan Meier method demonstrated poor event free survival for primary outcome in LVL-S (P = 0.002), and LVL-SI (P = 0.03). In Cox proportional hazard model, LVL-S (HR: 2.26, P = 0.004), and LVL-SI (1.9, P = 0.047) were independent predictors of primary outcome. CONCLUSION: In CRT recipients with ICM, scar and reversible ischemia in or adjacent to LV pacing site were independent predictors of HF hospitalization and death.

Interlead distance and left ventricular lead electrical delay predict reverse remodeling during cardiac resynchronization therapy.

BACKGROUND: Both anatomic interlead separation and left ventricle lead electrical delay (LVLED) have been associated with outcomes following cardiac resynchronization therapy (CRT). However, the relationship between interlead distance and electrical delay in predicting CRT outcomes has not been defined. METHODS: We studied 61 consecutive patients undergoing CRT for standard clinical indications. All patients underwent intraprocedural measurement of LVLED. Interlead distances in the horizontal (HD), vertical (VD), and direct (DD) dimensions were measured from postprocedure chest radiographs (CXR). Remodeling indices [percent change in left ventricle (LV) ejection fraction, end-diastolic, end-systolic dimensions] were assessed by transthoracic echocardiogram. RESULTS: There was a positive correlation between corrected LVLED and HD on lateral CXR (r = 0.361, P = 0.004) and a negative correlation between LVLED and VD on posteroanterior (PA) CXR (r =-0.281, P = 0.028). To account for this inverse relationship, we developed a composite anatomic distance (defined as: lateral HD-PA VD), which correlated most closely with LVLED (r = 0.404, P = 0.001). Follow-up was available for 48 patients. At a mean of 4.1 +/- 3.2 months, patients with optimal values for both corrected LVLED (>or=75%) and composite anatomic distance (>or=15 cm) demonstrated greater reverse LV remodeling than patients with either one or neither of these optimized values. CONCLUSIONS: We identified a significant correlation between LV-right ventricular interlead distance and LVLED; additionally, both parameters act synergistically in predicting LV anatomic reverse remodeling. Efforts to optimize both interlead distance and electrical delay may improve CRT outcomes.

Usefulness of low-dose dobutamine echocardiography to predict response and outcome in patients undergoing cardiac resynchronization therapy.

A substantial proportion of patients who meet the current guidelines for cardiac resynchronization therapy (CRT) fail to respond to this pacing modality. Although appropriate patient selection and left ventricular (LV) lead location have been ascribed as determinants of CRT response, the interaction among contractile reserve, dynamics of dyssynchrony, and lead location is not well understood. The present study prospectively evaluated the effect of contractile reserve and dobutamine-induced changes in LV synchrony, in relation to the LV lead location, as predictors of the response to CRT. In the present study, 31 patients were prospectively evaluated and underwent low-dose dobutamine echocardiography. The dobutamine-induced increase in ejection fraction (contractile reserve [CR]) was measured, and the most mechanically delayed segment was identified to classify patients into 2 groups. Group 1 had a CR of >20% and a LV lead position concordant with the mechanically delayed segment. Group 2 included the remaining patients (i.e., low CR, discordant LV lead position, or both). Patients in group 1 were significantly more likely to have an echocardiographic response at 6 months (80% of group 1 vs 29% of group 2, p = 0.018) and had an improved 2-year heart failure hospitalization-free survival rate (90% in group 1 vs 33% in group 2, p = 0.006). In conclusion, low-dose dobutamine echocardiography provides information that can help to predict responders to CRT. The response rates and heart failure hospitalization-free survival were improved in those patients with a CR >20% and an LV lead tip concordant with the most delayed mechanical segment.