The QRS complex—a biomarker that “images” the heart: QRS scores to quantify myocardial scar in the presence of normal and abnormal ventricular conduction☆

Typical left bundle branch block (LBBB) shows 2 peaks of the R wave, which reflect activation reaching the interventricular septum (R) and posterolateral wall (Rʹ) sequentially.

The purpose of this study was to investigate the relationship among R-Rʹ interval (RRʹ), mechanical dyssynchrony, extent of viable myocardium, and long-term outcomes in cardiac resynchronization therapy (CRT) candidates.

The study enrolled 49 patients (34 men; mean age: 69 ± 11 years) with LBBB who received CRT. The LBBB definition used requires the presence of mid-QRS notching in leads V₁, V₂, V₅, V₆, I, and aVL. Baseline evaluations were QRS duration (QRSd) and RRʹ measured from the 12-lead electrocardiogram; eyeball dyssynchrony (apical rocking and septal flash) and opposing-wall delay by speckle tracking from echocardiography, and extent of viable myocardium assessed by thallium-201 single-photon emission computed tomography. Primary outcomes included the combination of all-cause death and heart failure–related hospitalization.

RRʹ predicted volumetric response better than QRSd (area under the curve 0.73 vs 0.67, respectively). The long RRʹ group (≥48 ms) revealed more frequent eyeball dyssynchrony and significantly greater radial (SL) and circumferential dyssynchrony (AP and SL) and %viable segment than the short RRʹ group. In multivariate regression analysis, only RRʹ ≥48 ms was independently associated with higher event-free survival rates following CRT (hazard ratio 0.21; P = .014).

These findings suggest that RRʹ in complete LBBB was associated with mechanical dyssynchrony, extent of viable myocardium, and long-term outcomes following CRT.

The presence of an untreated chronic total coronary occlusion (CTO) is associated with a higher risk of ventricular arrhythmias (VAs). This increased risk may be modulated by the presence of an existing scar.

To evaluate whether scar size is associated with VA in patients with an implantable cardioverter-defibrillator (ICD) and a CTO.

In this retrospective study we included patients with a CTO that received an ICD between 2005 and 2015. Scar size was estimated using the Selvester QRS score on a baseline 12‑lead ECG. The primary endpoint was any appropriate ICD therapy.

Our study population comprised 148 CTO patients with a median scar size at baseline of 18% (IQR, 9–27%). Patients with a scar size ≥18% more often had a CTO located in the left anterior descending artery and a higher proportion of poor left ventricular function (<35%) and infarct-related CTO compared to patients with a smaller scar size (<18%). During a median follow-up of 35 months (interquartile range [IQR], 8–60 months), 42 patients (28%) received appropriate ICD therapy. The cumulative 5-year event rate was higher in the patients with a large scar in comparison to those with a smaller or no scar (36% versus 19%, P = 0.04). Multivariable Cox regression analysis demonstrated that large scar and diabetes mellitus were independent factors associated with appropriate ICD therapy.

In ICD recipients with an untreated CTO, a larger scar is an independent factor associated with an increased risk of VA.

A better selection of patients with left bundle branch block (LBBB) might increase the response to cardiac resynchronization therapy (CRT). The aim of the study was to investigate the association between the Strauss criteria, absence of S wave in V₅-V_6, the Selvester score and response to CRT.

The retrospective analysis included all consecutive patients having undergone implantation of biventricular defibrillators in primary prevention between 2018 and 2020.

The final analysis included 236 patients (mean age 69.7 ± 9.9; 77.5% of males). The Strauss criteria were significantly associated with CRT response (p < 0.01) with a sensitivity of 71.3% and specificity of 64.1%. The Strauss criteria along with the absence of S wave in V₅ and V₆ showed a sensitivity of 56.7%, a specificity of 82.6% and a positive predictive value of 90.5%. The Selvester score was significantly and inversely associated with CRT response (OR 0.818, 95% CI 0.75–0.89; p < 0.001). The multivariable model showed that left ventricular ejection fraction (LVEF) and QRS duration (≥140 ms in males and ≥ 130 ms in females) were independently associated with CRT response (respectively OR 0.92, CI 95% 0.86–0.98, p = 0.01 and OR 3.70, CI 95% 1.12–12.21, p = 0.03).

Strauss criteria, especially in association with absence of S wave in V₅ and V₆, were able to increase specificity and positive predictive value for predicting CRT response. The Selvester score was inversely associated with CRT response. Finally, LVEF and QRS duration were independently associated with echocardiographic response to CRT.

Chronic total occlusion (CTO) is a critical and unique subgroup of coronary lesions. This study aimed to investigate the correlation between the Selvester QRS score and late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMRI) in quantifying myocardial scarring to provide a simple and feasible method for treating CTO.

The medical records of 134 patients with absolute CTO who underwent coronary angiography between May 1, 2014 and December 30, 2017 were retrospectively reviewed. All patients were grouped according to the CTO location (RCA CTO, LAD CTO, LCX CTO, and multi-vessel CTO groups). The degree of myocardial scarring was determined according to the Selvester QRS score and using the LGE-CMRI. All patients were followed up for at least 12 months.

Among the 62 CTO patients, 55 had occlusion of a single vessel and seven had occlusion of multiple vessels, of which 27 (43.55%) were in the RCA CTO group, 16 (25.81%) in the LAD CTO group, 12 (19.35%) in the LCX CTO group, and 7 (11.29%) in the multi-vessel CTO group. The area under the receiver operating characteristic curve for the QRS score that was used to determine the degree of myocardial scarring was 0.806, with a sensitivity and specificity of 94.7% and 42.1%, respectively. The Selvester QRS score and LGE-CMRI measures of scar size were correlated in the RCA CTO, LCX CTO, and multi-vessel CTO groups (r = 0.466, 0.593, and 0.775, respectively).

The Selvester QRS score was feasible for detecting myocardial scarring in patients with CTO.

Whether the electrocardiography (ECG) serial changes predict outcomes in cardiac arrest survivors undergoing therapeutic hypothermia remains unclear.

This retrospective observational study enrolled 366 adult nontraumatic cardiac arrest survivors who underwent therapeutic hypothermia in a tertiary transfer center during 2006–2018. The ECG at return of spontaneous circulation (ROSC), during hypothermia and after rewarming were analyzed. 295 cardiac arrest survivors were included. Compared with the survivors, the non-survivors had longer QRS durations at the ROSC (118.33 ± 32.47 ms vs 106.88 ± 29.78 ms, p < 0.001) and after rewarming (99.26 ± 25.07 ms vs 93.03 ± 19.09 ms, p = 0.008). The enrolled patients were classified into 4 groups based on QRS duration at the ROSC and after rewarming, namely (1) narrow–narrow (narrow QRS at ROSC and narrow QRS after rewarming, n = 156), (2) narrow–wide (n = 29), (3) wide–narrow (n = 87), and (4) wide–wide (n = 23) group. The wide–wide group had the worst survival rates [odds ratio (OR) = 0.141, p = 0.001], followed by the narrow–wide group (OR 0.223, p = 0.003) and the wide–narrow group (OR 0.389, p = 0.003).

In cardiac arrest survivors given therapeutic hypothermia, QRS durations at the ROSC, after rewarming and their changes may predict survival to hospital discharge.