Interatrial Block Predicts Life-Threatening Arrhythmias in Dilated Cardiomyopathy

Abstract

Background Interatrial block (IAB) has been associated with supraventricular arrhythmias and stroke, and even with sudden cardiac death in the general population. Whether IAB is associated with life-threatening arrhythmias (LTA) and sudden cardiac death in dilated cardiomyopathy (DCM) remains unknown. This study aimed to determine the association between IAB and LTA in ambulant patients with DCM. Methods and Results A derivation cohort (Maastricht Dilated Cardiomyopathy Registry; N=469) and an external validation cohort (Utrecht Cardiomyopathy Cohort; N=321) were used for this study. The presence of IAB (P-wave duration>120 milliseconds) or atrial fibrillation (AF) was determined using digital calipers by physicians blinded to the study data. In the derivation cohort, IAB and AF were present in 291 (62%) and 70 (15%) patients with DCM, respectively. LTA (defined as sudden cardiac death, justified shock from implantable cardioverter-defibrillator or anti-tachypacing, or hemodynamic unstable ventricular fibrillation/tachycardia) occurred in 49 patients (3 with no IAB, 35 with IAB, and 11 patients with AF, respectively; median follow-up, 4.4 years [2.1; 7.4]). The LTA-free survival distribution significantly differed between IAB or AF versus no IAB (both P<0.01), but not between IAB versus AF (P=0.999). This association remained statistically significant in the multivariable model (IAB: HR, 4.8 (1.4-16.1), P=0.013; AF: HR, 6.4 (1.7-24.0), P=0.007). In the external validation cohort, the survival distribution was also significantly worse for IAB or AF versus no IAB (P=0.037; P=0.005), but not for IAB versus AF (P=0.836). Conclusions IAB is an easy to assess, widely applicable marker associated with LTA in DCM. IAB and AF seem to confer similar risk of LTA. Further research on IAB in DCM, and on the management of IAB in DCM is warranted.

Keywords: dilated cardiomyopathy; electrocardiography; interatrial block; life‐threatening arrhythmias; non‐ischemic cardiomyopathy; sudden cardiac death.

Figure 1. Patient selection for this retrospective analysis performed within the Maastricht Dilated Cardiomyopathy Registry.

All patients presented between 2004 and 2017 at the DCM outpatient clinic (OC) in the Maastricht University Medical Center. *Baseline ECG: ECG closest to OC (at the latest 1 month before or after OC). AF indicates atrial fibrillation; DCM, dilated cardiomyopathy; and IAB, interatrial block.

Figure 2. Kaplan–Meier curves of survival free of life‐threatening arrhythmias performed within the Maastricht Dilated Cardiomyopathy cohort.

A, stratified by No interatrial block (IAB), IAB, and Atrial Fibrillation (AF). The survival distribution between the groups was significantly different (P=0.003, χ ²=11.5). This difference was significantly different for both IAB or AF vs No IAB (P=0.006 and P=0.001, respectively), but not for IAB vs AF (P=0.999) after applying Bonferroni correction. B, stratified by No interatrial block (IAB), Partial IAB, Advanced IAB, and Atrial Fibrillation (AF). The survival distribution between the groups was significantly different (P=0.006). This difference was significantly different for Partial IAB, Advanced IAB or AF vs No IAB (P=0.032 and P=0.005, 0.003, respectively), but not for Partial IAB vs Advanced IAB (P=0.999) after applying Bonferroni correction.

Figure 3. Univariable overview of hazard ratios (HR) for the study end point (life‐threatening arrhythmias).

ACEi indicates angiotensin‐converting enzyme inhibitor; AF, atrial fibrillation; ARB, angiotensin receptor blocker; BMI, body mass index; bpm, beats per minute; DBP, diastolic blood pressure; DCM, dilated cardiomyopathy; DM, diabetes; FH CMP, self‐reported family history of cardiomyopathy; HFH, heart failure hospitalization; HR, heart rate; IAB, inter‐atrial block; LAVI, left atrial volume index; LVEDDI, left ventricular end‐diastolic diameter indexed by body surface area; LVEF, left ventricular ejection fraction; LVH, left ventricular hypertrophy (LVMI≥95 in female patients or LVMI≥115 in male patients); LVMI, left ventricular mass indexed by body surface area; MRA, mineralocorticoid receptor antagonist; NT‐proBNP, N‐terminal‐pro hormone Brain Natriuretic Peptide; NYHA, New York Heart Association classification; OMT, percentage of optimal medical heart failure therapy in line with the ESC 2016 guidelines; ref, reference; and SBP, systolic blood pressure.

Figure 4. Multivariable overview (applying backward selection) of hazard ratios (HR) for the study end point (life‐threatening arrhythmias).

A, P‐morphology stratified as No IAB (PWD≤120 ms), IAB (PWD>120 ms), or AF. B, P morphology stratified as No IAB (PWD≤120 ms), Partial IAB (PWD>120 ms), Advanced IAB (PWD>120 ms AND biphasic morphology of P‐wave in leads II, III and aVF as previously described; patients with biphasic morphology of P‐wave in at least III and aVF were also included in this group) or AF. AF indicates atrial fibrillation; FH CMP, self‐reported family history of dilated cardiomyopathy; IAB, inter‐atrial block; LVH, left ventricular hypertrophy (LVMI≥95 in female patients or LVMI≥115 in male patients); PWD, P‐wave duration; and ref, reference.

Figure 5. Kaplan–Meier curves of survival free of life‐threatening arrhythmias performed within the Utrecht Cardiomyopathy cohort (UNRAVEL).

A, stratified by No interatrial block (IAB), IAB, and atrial fibrillation (AF). The survival distribution between the groups was significantly different (P=0.008, χ ²=9.7). This difference was significantly different for both IAB or AF vs No IAB (P=0.037 and P=0.005, respectively), but not for IAB vs AF (P=0.836) after applying Bonferroni correction. B, stratified by No interatrial block (IAB), Partial IAB, Advanced IAB and AF. The survival distribution between the groups was significantly different (P=0.004). This difference was significantly different for Advanced IAB or AF vs No IAB (P=0.009 and P=0.010, respectively), but not for Partial IAB vs No IAB (P=0.211) and Partial vs Advanced IAB (P=0.473), after applying Bonferroni correction.

Figure 6. Interatrial block (IAB) and atrial fibrillation (AF) assessed at baseline ECG confer similar increased risk of life‐threatening arrhythmias (LTAs) in ambulant patients with dilated cardiomyopathy (DCM) in 2 independent cohorts (The Maastricht DCM Cohort and The Utrecht Cardiomyopathy Cohort, UNRAVEL).

The survival distribution was significantly different for the 3 groups in both cohorts (P=0.003 Maastricht; P=0.008 Utrecht). This difference was significantly different for both IAB and AF vs No IAB, but not for IAB vs AF. *=monophasic P‐wave;**=bi‐phasic P‐wave. PWD indicates P‐wave duration.