Key result
CAP2 deficiency increases inducible ventricular tachycardia to 88% and causes marked conduction delays in mice.
Why the study?
CAP2 inactivation in mice results in cardiomyopathy and increased mortality, suggesting a major impact on arrhythmias and electrophysiological parameters that requires investigation.
Does CAP2 deficiency promote arrhythmias and alter electrophysiological parameters in a mouse model?
Does CAP2 deficiency promote arrhythmias and alter electrophysiological parameters in a mouse model?
Absolute Event Rate: 88% vs 33%
p-value: p=0.04
Loss of CAP2 in mice leads to impaired sinus node function, conduction delays, increased susceptibility to malignant arrhythmias, and structural changes including fibrosis and connexin43 maldistribution.
CAP2 deficiency promotes ventricular arrhythmias in mice; leaves open relevance to human arrhythmogenesis pending translational studies.
INTRODUCTION: Cyclase-associated protein 2 (CAP2) plays a major role in regulating the actin cytoskeleton. Since inactivation of CAP2 in a mouse model by a gene trap approach (Cap2 (gt/gt) ) results in cardiomyopathy and increased mortality, we hypothesized that CAP2 has a major impact on arrhythmias and electrophysiological parameters. MATERIAL AND METHODS: We performed long-term-ECG recordings in transgenic CAP2 deficient mice (C57BL/6) to detect spontaneous arrhythmias. In vivo electrophysiological studies by right heart catheterization and ex vivo epicardial mapping were used to analyze electrophysiological parameters, the inducibility of arrhythmias, and conduction velocities. Expression and distribution of cardiac connexins and the amount of cardiac fibrosis were evaluated. RESULTS: Spontaneous ventricular arrhythmias could be detected in Cap2 (gt/gt) during the long-term-ECG recording. Cap2 (gt/gt) showed marked conduction delays at atrial and ventricular levels, including a reduced heart rate (421.0 ±40.6 bpm vs. 450.8 ±27.9 bpm; p < 0.01), and prolongations of PQ (46.3 ±4.1 ms vs. 38.6 ±6.5 ms; p < 0.01), QRS (16.2 ±2.6 ms vs. 12.6 ±1.4 ms; p < 0.01), and QTc interval (55.8 ±6.0 ms vs. 45.2 ±3.3 ms; p = 0.02) in comparison to wild type mice. The PQ prolongation was due to an infra-Hisian conduction delay (HV: 9.7 ±2.1 ms vs. 6.5 ±3.1 ms; p = 0.02). The inducibility of ventricular tachycardias during the electrophysiological studies was significantly elevated in the mutant mice (inducible animals: 88% vs. 33%; p = 0.04). Cap2 (gt/gt) showed more abnormal distribution of connexin43 compared to WT (23.0 ±4.7% vs. 2.9 ±0.8%; p < 0.01). Myocardial fibrosis was elevated in Cap2 (gt/gt) hearts (9.1 ±6.7% vs. 5.5 ±3.3%; p < 0.01). CONCLUSIONS: Loss of CAP2 results in marked electrophysiological disturbances including impaired sinus node function, conduction delays, and susceptibility to malignant arrhythmias. Structural changes in Cap2 (gt/gt) are associated with alterations in myocardial connexins and fibrosis.
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Stöckigt et al. (2016) studied Arrhythmias and Cardiomyopathy (n=33). CAP2 deficiency (Cap2 gt/gt) vs. Wild type (WT) mice was evaluated on Inducibility of ventricular tachycardias (p=0.04). Homozygous CAP2 deficiency in mice significantly increased the inducibility of ventricular tachycardias compared to wild-type controls (88% vs. 33%, p=0.04) and resulted in marked conduction delays.
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