His-cardiac resynchronization therapy (CRT) did not demonstrate significant improvements in electrocardiographic or echocardiographic parameters as compared to biventricular pacing (BiV) CRT, according to research presented May 9 at the Heart Rhythm Scientific Sessions in San Francisco, and simultaneously published in the Journal of the American College of Cardiology.

Gaurav A. Upadhyay, MD, FACC, et al., randomized 41 patients aged >18 years meeting guideline indications for CRT to His-CRT or coronary sinus lead for BiV-CRT with routine implantation techniques. Crossover was mandated in patients in the His-CRT group who did not achieve QRS narrowing by >20 percent, QRS width of ≤130 ms, or who demonstrated high correction thresholds (>5V@1 ms). While crossover was permitted in patients randomized to BiV-CRT when an LV lead could not be placed, LV lead delivery into the anterior interventricular or middle cardiac veins was discouraged.

Overall results showed no differences in baseline characteristics across the two groups, with the exception that LVEF was significantly lower in the His-CRT group (median 26.3 percent) compared to the BiV-CRT (30.5 percent). Researchers noted that crossover occurred in 48 percent of His-CRT patients and 26 percent of BiV-CRT patients, due primarily to the inability to correct QRS (n=5) in the His-CRT group and suboptimal venous anatomy (n=4) in the BiV-CRT group. Significant reduction in QRS duration was also observed in the His-CRT group, but not the BiV-CRT group.

In other findings, at a median follow-up of 6.2 months, improvements in LVEF relative to baseline were observed patients in both groups. Overall event rates were also low across both groups (6 cardiovascular hospitalizations, 2 deaths). Additionally, QLV was reported in 20 of 24 patients receiving BiV across both arms. Patients in the His-CRT had higher pacing thresholds (median 1.7 V vs. 0.9 V), but not pulse width (median 1 ms vs. 0.5 ms), compared with BiV-CRT patients. His corrective capture thresholds remained stable in up to 12 months of follow-up.

Tung and colleagues noted that the study was underpowered to detect differences less than 10 percent between groups and a type II error cannot be excluded. They suggest that "improved patient selection may decrease crossover rates and larger prospective studies may be useful to assess for smaller differences in effect size between CRT modalities."

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Echocardiography/Ultrasound

Keywords: Cardiac Resynchronization Therapy, Aleurites, Coronary Sinus, Patient Selection, Electrocardiography, Echocardiography, Heart Rate, Hospitalization, Arrhythmias, Cardiac

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