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Updated: Aug 17, 2026
Electromechanical Assessment of Optogenetically Modulated Cardiomyocyte Activity
Published on: March 5, 2020
Pacing-induced electrophysiological remodeling in hypertrophic obstructive cardiomyopathy--observations on cardiac
Karolina Nowinski1, Liliane Wecke, Fredrik Gadler
1Department of Cardiology, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
Insights
Pacing in hypertrophic obstructive cardiomyopathy (HOCM) patients shortens repolarization despite prolonged activation. Cardiac memory responses differ based on patient electrophysiology, impacting pacing outcomes.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Hypertrophic cardiomyopathy (HCM) increases sudden cardiac death risk.
- Pacing therapy can improve symptoms and reduce gradients in hypertrophic obstructive cardiomyopathy (HOCM).
- Electrophysiological effects of pacing in HOCM remain largely unknown.
Purpose of the Study:
- To assess the electrophysiological consequences of DDD pacing in HOCM patients.
- To investigate cardiac memory development and repolarization changes during pacing in HOCM.
Main Methods:
- Prospective study comparing 15 HOCM patients with 14 controls undergoing DDD pacing.
- ECG intervals measured pre- and post-pacemaker implantation.
- Analysis of cardiac memory and repolarization parameters (QTc, JTc, QRS duration).
Main Results:
- Both HOCM and control groups showed cardiac memory development.
- HOCM patients had no significant QTc interval changes with pacing.
- HOCM patients exhibited shorter repolarization (JTc) during pacing despite prolonged QRS duration.
Conclusions:
- Cardiac memory induces varied repolarization responses in HOCM patients.
- Right ventricular apical pacing in HOCM results in shorter repolarization compared to sinus rhythm.
- Pacing's electrophysiological effects in HOCM are distinct and depend on individual cardiac structure and electrophysiology.
Background:
Hypertrophic cardiomyopathy carries an increased risk for sudden cardiac death. While pacing therapy reduces the left ventricular outflow tract gradient and improves symptoms in a subgroup of hypertrophic obstructive cardiomyopathy (HOCM) patients, its electrophysiological consequences are unknown and were therefore assessed in this prospective study.
Methods And Results:
Fifteen consecutive HOCM patients were studied and compared with 14 patients without HOCM paced because of sinus bradycardia. ECG intervals were measured before pacemaker implantation and after > or =3 months of DDD pacing in HOCM patients and > or =5 weeks in controls. Both groups showed similar ECG signs of cardiac memory development. In HOCM patients, with baseline QTc 447 +/- 33 ms, cardiac memory development was not associated with any significant changes in ECG intervals. In contrast, baseline repolarization in control patients was significantly prolonged by 6% (QTc 429 +/- 33 vs 454 +/- 46 ms; P < 0.05). Furthermore, in HOCM patients repolarization was 7% shorter during DDD pacing compared to sinus rhythm (JTc 329 +/- 25 vs 353 +/- 21 ms; P < 0.05), despite a significantly prolonged ventricular activation time (QRS duration 155 +/- 16 vs 91 +/- 9 ms; P < 0.01).
Conclusions:
Importantly, the development of cardiac memory-induced different repolarization responses depending on baseline structure and electrophysiology. In HOCM patients repolarization was shorter during right ventricular apical pacing than during normal activation despite prolonged activation time.
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