Acute induction of sustained ventricular tachycardia: a new porcine model

In this study we evaluated the possibility of initiating long-lasting ventricular tachycardias acutely, using isolated porcine hearts and thus avoiding an open-chest operation model. This set-up was designed especially to investigate defibrillating or antitachycardiac pacing devices, which terminate these malignant arrhythmias if medical treatment fails. The experiments were performed on 42 pigs, weighing 20-25 kg. After thoracotomy their hearts were removed and adapted to a Langendorff perfusion system. Supplied with their own blood, beating hearts were manipulated in three different ways: direct current impulses (4.5 V, 750 ms) or programmed ventricular stimulation, creation of a small myocardial infarction, and application of antiarrhythmic drugs (ajmalin, lidocaine, sotalol). Out of all possibilities the combination of ajmalin (mean concentration 0.041 micrograms/ml) and a small anteroapical myocardial infarction (3-6 cm2) along with direct current impulses (4.5 V), led to sustained ventricular tachycardias in the highest proportion (93%) of trials (P less than 0.001). The heart rate was 251 beats per minute on average. Lidocaine trials were less successful (53%), while programmed ventricular stimulation and sotalol failed to induce ventricular tachycardias. This study supports the evidence that the combination of ajmalin and a small myocardial infarction with direct current impulses is a reliable model for sustained ventricular tachycardias in isolated pig hearts. Although it is a rather artificial organ model, tachycardias can be induced acutely without any long-term pretreatment. Animal models based on chronic myocardial infarctions will therefore be unnecessary for the investigation of defibrillating systems and antitachycardiac pacing devices.