Left atrial volume and function measured by cardiac magnetic resonance imaging as predictors of shocks and mortality in patients with implantable cardioverter-defibrillators.

Left atrial (LA) volume and function (LA ejection fraction, LAEF) have demonstrated prognostic value in various cardiovascular diseases. We investigated the incremental value of LA volume and LAEF as measured by cardiovascular magnetic resonance imaging (CMR) for prediction of appropriate implantable cardioverter defibrillator (ICD) shock or all-cause mortality, in patients with ICD. We conducted a retrospective, multi-centre observational cohort study of patients who underwent CMR prior to primary or secondary prevention ICD implantation. A single, blinded reader measured maximum LA volume index (maxLAVi), minimum LA volume index (minLAVi), and LAEF. The primary outcome was a composite of independently adjudicated appropriate ICD shock or all-cause death. A total of 392 patients were enrolled. During a median follow-up time of 61 months, 140 (35.7%) experienced an appropriate ICD shock or died. Higher maxLAVi and minLAVi, and lower LAEF were associated with greater risk of appropriate ICD shock or death in univariate analysis. However, in multivariable analysis, LAEF (HR 0.92 per 10% higher, 95% CI 0.81-1.04, p = 0.17) and maxLAVi (HR 1.02 per 10 ml/m2 higher, 95% CI 0.93-1.12, p = 0.72) were not independent predictors of the primary outcome. In conclusion, LA volume and function measured by CMR were univariate but not independent predictors of appropriate ICD shocks or mortality. These findings do not support the routine assessment of LA volume and function to refine risk stratification to guide ICD implant. Larger studies with longer follow-up are required to further delineate the clinical implications of LA size and function.

Cardiac remodeling in middle-aged endurance athletes: relation between signal-averaged electrocardiogram and LV mass.

The relationship between structural and electrical remodeling in the heart, particularly after long-standing endurance training, remains unclear. Signal-averaged electrocardiogram (SAECG) may provide a more sensitive method to evaluate cardiac remodeling than a 12-lead electrocardiogram (ECG). Accurate measures of electrical function (SAECG filtered QRS duration (fQRSd) and late potentials (LP) and left-ventricular (LV) mass (cardiac magnetic resonance, CMR) can allow an assessment of structural remodeling and QRS prolongation. Endurance athletes (45-65 yr old, >10 yr of endurance sport), screened to exclude cardiac disease, had standardized 12-lead ECG, SAECG, resting echocardiogram (ECHO), and CMR performed. SAECG fQRSd was correlated with QRS duration on the 12-lead ECG, and ECHO and CMR-derived LV mass. Participants (n = 82, 67% male, mean age: 54 ± 6 yr, mean V̇o2max: 50 ± 7 mL/kg/min) had a CMR-derived LV mass of 118 ± 28 g/m2 and a fQRSd of 112 ± 8 ms (46% had abnormal fQRSd (>114 ms), and 51% met clinical threshold for abnormal SAECG). fQRSd was positively correlated with the 12-lead ECG QRS duration (r = 0.83), ECHO-derived LV mass (r = 0.60), CMR-derived LV mass (r = 0.58) and LV end-diastolic volume (r = 0.63, P < 0.001 for all). fQRSd had higher correlations with ECHO and CMR-derived LV mass than 12-lead ECG (P < 0.0008 and P < 0.0005, respectively). In conclusion, in a healthy cohort of middle-aged endurance athletes, the SAECG is often abnormal by conventional criteria, and is correlated with structural remodeling, but CMR evaluation does not indicate pathologic structural remodeling. SAECG fQRSd is superior to the 12-lead ECG for the electrocardiographic evaluation of LV mass.NEW & NOTEWORTHY Study findings indicate that a positive correlation exists between electrical (SAECG fQRSd) and structural indices (LV mass) in middle-aged endurance athletes with normal physiological LV adaptation, in the absence of known cardiac pathology. SAECG fQRSd may also provide an alternative, superior method for identifying increased LV mass compared to other 12-lead ECG criteria.