Low room temperature can trigger ventricular fibrillation in J wave syndromes

J wave syndrome: Benign or malignant?

J wave syndrome is an electrical disease of the heart due to pathologic early repolarization. It encompasses a clinical spectrum from aborted sudden cardiac death due to ventricular arrhythmia (VA) usually in young affected patients to self-terminating ventricular ectopies, and finally, asymptomatic relatives of probands detected during electrocardiography acquisition (early repolarization pattern). This syndrome consists of 2 phenotypes, early repolarization and Brugada syndrome. Herein, we first describe 2 patients with early repolarization and Brugada syndrome, then, discuss their definition, epidemiology, genetics, cellular mechanism, diagnosis, risk stratification, and finally, therapeutic challenges and options one by one in detail.

The AMP-activated protein kinase modulates hypothermia-induced J wave

BACKGROUND

The mechanism underlying the occurrence of the J wave in low temperature remains unclear. However, low temperature is associated with metabolic disorder and 5' AMP-activated protein kinase (AMPK), which modulates ionic currents and cardiac metabolism. This study investigated whether AMPK regulation can modulate the occurrence of the J wave at low temperature.

METHODS

Unipolar and bipolar leads were used to record monophasic action potential (the endocardium and epicardium) and pseudo-electrocardiograms (inferior leads) to study the cardiac electrical activity. Measurements were taken in isolated Langendorff rabbit hearts at both 30℃ and 37℃ before and after administration of 4-aminopyridine (an ultrarapid delayed rectifier potassium current inhibitor, I_Kur , 50 µmol L^-1 ), PF06409577 (an AMPK activator, 1 µmol L^-1 ), compound C (an AMPK inhibitor, 10 µmol L^-1 ) and glibenclamide (an ATP-sensitive inward rectifier potassium channel inhibitor, I_KATP , 20 µmol L^-1 ).

RESULTS

The amplitude of the J wave (2.46 ± 0.34 mV vs. 1.11 ± 0.23 mV, P < .01) at 30℃ (n = 15) was larger than that at 37℃ (n = 15). PF06409577 (1 µmol L^-1 ) increased the J waves at both 30℃ and 37℃. In contrast, compound C (10 µmol L^-1 ) reduced J wave at both 37℃ and 30℃. Low-temperature-induced J waves were individually suppressed by 4-AP (50 µmol L^-1 ) and glibenclamide (20 µmol L^-1 ).

CONCLUSIONS

AMPK inhibition reduces low-temperature-induced J waves and possible ventricular arrhythmogenesis by modulating I_KATP and I_Kur channels.

Epinephrine-induced electrical storm after aortic surgery

Electrical storm (ES) is a potentially lethal syndrome defined as three or more sustained episodes of ventricular tachycardia or ventricular fibrillation within 24 h. There are multiple inciting factors for ES, one of which involves excess catecholamine (endogenous and exogenous) effects. Exogenous catecholamines used for hemodynamic support can paradoxically engender or exacerbate an underling arrhythmia leading to ES. We report on an 63-year-old man who presented for repair of an ascending aortic dissection. After cardiopulmonary bypass separation assisted with high-dose epinephrine, ES developed requiring over 40 defibrillatory shocks. The epinephrine infusion was held and within 5 min, the ES self-terminated. ES in the context of cardiovascular surgery with the use of epinephrine for hemodynamic support has not be previously reported. Clinicians need to be cognizant of the seemingly paradoxical effect of epinephrine to induce ES. Initial ES treatment involves acute stabilization (treating or removing exacerbating factors (i.e., excess catecholamines)).

Case report: electrical storm during induced hypothermia in a patient with early repolarization

Background

Population based studies showed an association of early repolarization in the electrocardiogram (ECG) and a higher rate of sudden cardiac death presumably due to ventricular fibrillation. The triggers for ventricular fibrillation in patients with early repolarization are not fully understood.

Case presentation

We describe the case of a young patient with a survived ventricular fibrillation arrest while asleep followed by multiple episodes of recurrent ventricular fibrillation. The admission ECG showed an early repolarization pattern with substantial J-point elevation in most of the ECG-leads. After initiation of a hypothermia protocol, the patient developed an electrical storm with multiple ventricular fibrillation episodes requiring multiple cardioversions. Intravenous isoproterenol infusion successfully suppressed the malignant arrhythmia.

Conclusion

Hypothermia appears proarrhythmic in patients with early repolarization and may trigger ventricular fibrillation. This knowledge is particularly important when initiating temperature management protocols in patients after a survived cardiac arrest. During the acute phase of an early repolarization associated electrical storm, isoproterenol is the most effective treatment suppressing the ventricular fibrillation-inducing premature ventricular complexes at higher heart rates.