The differentiation of propafenone from other class Ic agents, focusing on the effect on ventricular response rate attributable to its beta-blocking action

Old stuff still trending: use of propafenone as a safety net until catheter ablation in a patient with documented pre-excited atrial fibrillation and Wolff-Parkinson-White syndrome - a classic case report

BACKGROUND

Atrial fibrillation in Wolff-Parkinson-White syndrome may result in life-threateningly rapid antegrade conduction over a bypass tract, manifested by an irregular broad-complex (pre-excited) tachycardia that can degenerate to ventricular fibrillation. The shortest pre-excited RR interval below 250 ms during atrial fibrillation (AF) predicts increased risk of sudden cardiac death.

CASE SUMMARY

We report a case of a 43-year-old man with unremarkable cardiac history who presented due to sudden-onset feeling of palpitations and pre-syncope after strenuous lifting. Electrocardiography depicted fast pre-excited AF. The shortest pre-excited RR interval was estimated at 160 ms, indicating an accessory pathway (AP) with short antegrade refractory period at risk for mediating sudden cardiac death. Direct current cardioversion restored sinus rhythm unravelling delta waves. The patient was put on propafenone 450 mg/day having an uneventful clinical course. On Day 10 post-admission, electrophysiological study induced rapid AF but the shortest pre-excited RR interval was substantially increased to 264 ms. A left anterolateral AP was ablated. The patient remained symptom free until his latest follow-up in the 3rd-month post-ablation without manifest pre-excitation on the surface electrocardiogram.

DISCUSSION

Treatment options of pre-excited AF include anti-arrhythmic agents but mainly electrical cardioversion. Cardioversion can safely restore sinus rhythm, while use of anti-arrhythmics often requires intensive care unit monitoring due to the risk of QT prolongation. Catheter ablation is the mainstay of therapy for symptomatic patients. Our rare report highlights the direct impact of propafenone on prolonging the refractoriness of the AP, effectively and safely, and reappraises propafenone's worthiness as a protective measure following pre-excited AF episode until ablation.

Cardioprotective effect of glucose-insulin on acute propafenone toxicity in rat

OBJECTIVE

We recently observed a case of propafenone self-poisoning in which the patient was initially unresponsive to conventional therapies such as sodium bicarbonate, dopamine, and norepinephrine but recovered with intravenous glucose-insulin infusion. We raised the hypothesis that insulin may have a cardioprotective effect in acute propafenone toxicity.

METHODS

We evaluated the effect of glucose-insulin infusion on mortality and electrocardiographic abnormalities during acute propafenone toxicity in rats. After measurements of basal mean arterial pressure, heart rate, PR interval, and QRS duration, rats received intravenous propafenone (36 mg/kg per hour) for 12 minutes. Two minutes after the induction of toxicity, the rats (n=10 per group) received either normal saline solution (NSS) or insulin with glucose. Rats in the insulin-treated (Insulin group) and the NSS-treated (NSS group) groups received an intravenous infusion of 36 mg/kg per hour of propafenone until death occurred. Rats receiving only NSS intravenously without propafenone toxicity served as control (Control group, n=10).

RESULTS

Insulin treatment improved survival and delayed the hemodynamic and electrocardiographic consequences of propafenone toxicity. Survival was significantly greater in the insulin group than that in the NSS group (P<.001). Insulin prevented the decline in mean arterial pressure and heart rate (P<.05). Insulin also prevented the increase of the PR interval and the QRS duration (P<.05).

CONCLUSION

Glucose-insulin infusion delayed the abnormalities in cardiac conduction and improved rat survival after acute propafenone toxicity. These results suggest a cardioprotective effect of glucose-insulin in acute propafenone toxicity.

Drugs, their targets and the nature and number of drug targets

What is a drug target? And how many such targets are there? Here, we consider the nature of drug targets, and by classifying known drug substances on the basis of the discussed principles we provide an estimation of the total number of current drug targets.