Category Archives: Arrhythmias

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 9)

While conditioning the ventricles for torsades de pointes by inducing bradycardia and prolonging QTc, favouring triggered activity , no spontaneous arrhythmias were observed. Interestingly, at the end of the experiments electrical stimulation during T wave of these conditioned ventricles induced … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 8) / ventolin 100 mcg

The question arises as to whether channels other than sodium channels are affected by the drugs used. DPI 201-106 starts to inhibit potassium channels at 3 |j.mol and calcium channels at 1.6 |j.mol in guinea-pig ventricular myocytes. Because we applied … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 7)

For the pharmacological induction of substantial QTc prolongation we employed the sodium channel ligands DPI 201-106 and veratridine in combination. Both veratridine and DPI 201-106 inhibit cardiac sodium channel inactivation and hence prolong action potential duration, as do various other … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 6)

No toxic effects and no spontaneous arrhythmias were recorded because all preparations remained in a stable condition throughout the experiment. At the end of the experiments ventricles treated with DPI 201-106 plus veratridine responded to electrical stimulation with torsade de … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 5)

Perfusion of ventricular preparations with Tyrode’s solution containing DPI 201-106 0.5 |iM plus veratridine 0.5 |iM decreased heart rate, and increased QTc and force of contraction in a statistically significant manner, as shown in Figure 2. The most drastic effects … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 4)

RESULTS Hearts were first perfused in sinus rhythm with normal Tyrode’s solution for comparison. As shown in Figure 1, heart rate decreased continuously from 195±4 beats/min to 161±6 beats/min after 170 mins. This small decline was statistically significant from 90 … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 3)

The stabilization period lasted at least 30 mins before any drug infusion. Endocardial ECG was derived from the right ventricle by means of a small bipolar catheter introduced via the pulmonary artery. Force of contraction was measured within the left … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 2)

ANIMALS AND METHODS Experiments were performed in adult Tricolor guinea-pigs of both sexes weighing between 500 and 600 g with free access to food and water. The animals were stunned by a blow on the neck and exsanguinated by opening … Continue reading

Conditioning guinea-pig hearts in vitro for torsade de pointes arrhythmias (part 1)

Torsades de pointes are ventricular polymorphic tachycardias with a typical turn of the R peaks in the electrocardiogram (ECG) as first described by Dessertenne . The danger of torsades de pointes is their tendency to degenerate into ventricular fibrillation . … Continue reading