Key result
In Japanese patients receiving cardiac resynchronization therapy, the response rate did not differ significantly among those with narrow (<130 ms), mid (130-150 ms), and wide (≥150 ms) QRS durations (83.6%, 91.3%, and 92.4%, respectively).
Why the study?
Variation in human body sizes may affect QRS duration, leading to the hypothesis that conduction disturbances and potential CRT candidacy exist in Japanese patients even with a narrow QRS complex (< 130 ms).
Does a narrow QRS duration (<130 ms) still allow for response to cardiac resynchronization therapy in lightweight Japanese patients?
Observational (n=537)
No
Does a narrow QRS duration (<130 ms) still allow for response to cardiac resynchronization therapy in lightweight Japanese patients?
Absolute Event Rate: 83.6% vs 92.4%
In Japanese patients, QRS duration depends on body size, and CRT response rates remain high even in patients with a narrow QRS (<130 ms), suggesting a strict >130 ms cutoff may not be necessary for smaller patients.
High CRT response in narrow-QRS Japanese patients may support body size-adjusted thresholds; leaves open prospective validation before practice change.
A prolonged QRS duration (QRSd) is promising for a response to cardiac resynchronization therapy (CRT). The variation in human body sizes may affect the QRSd. We hypothesized that conduction disturbances may exist in Japanese even with a narrow (< 130 ms)-QRS complex; such patients could be CRT candidates. We investigated the relationships between QRSd and sex and body size in Japanese. We retrospectively analyzed the values of 338 patients without heart failure (HF) (controls) and 199 CRT patients: 12-lead electrocardiographically determined QRSd, left ventricular diastolic and systolic diameters (LVDd and LVDs), body surface area (BSA), body mass index (BMI), and LVEF. We investigated the relationships between the QRSd and BSA, BMI, and LVD. The men’s and women’s BSA values were 1.74 m 2 and 1.48 m 2 in the controls ( p < 0.0001), and 1.70 m 2 and 1.41 m 2 in the CRT patients ( p < 0.0001). The men’s and women’s QRSd values were 96.1 ms and 87.4 ms in the controls ( p < 0.0001), and 147.8 ms and 143.9 ms in the CRT group ( p = 0.4633). In the controls, all body size and LVD variables were positively associated with QRSd. The CRT response rate did not differ significantly among narrow-, mid-, and wide-QRS groups (83.6%, 91.3%, 92.4%). An analysis of the ROC curve provided a QRS cutoff value of 114 ms for CRT responder. The QRSd appears to depend somewhat on body size in patients without HF. The CRT response rate was better than reported values even in patients with a narrow QRSd (< 130 ms). When patients are considered for CRT, a QRSd > 130 ms may not be necessary, and the current JCS guidelines appear to be appropriate.
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Nakai et al. (2019) conducted an observational in Heart failure (CRT candidates) (n=537). Narrow QRS duration (<130 ms) vs. Mid (130-150 ms) and wide (≥150 ms) QRS duration was evaluated on CRT response rate (functional and echocardiographic improvement at 6 months). In Japanese patients receiving cardiac resynchronization therapy, the response rate did not differ significantly among those with narrow (<130 ms), mid (130-150 ms), and wide (≥150 ms) QRS durations (83.6%, 91.3%, and 92.4%, respectively).
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