Usual site of origin of idiopathic ventricular tachycardia are the fascicles of the left bundle. A group of investigators from University of Alabama at Birmingham, USA have described tachycardia originating from both the anterior  and posterior  papillary muscles of the left ventricle.
Anterior papillary muscle tachycardia
Tachycardias may arise from the base or middle of the anterior papillary muscle and manifest with a right bundle branch block pattern with right inferior axis of the QRS complex. There was no response to oral verapamil or sodium channel blockers. No Purkinje potentials were recorded in these cases. These tachycardias could not be induced by programmed stimulation. They have a focal mechanism and catheter ablation may be difficult because it needs creation of deep lesions. Four of the six patients had long term success following ablation with an 8 mm irrigated tip radiofrequency ablation catheter.
Posterior papillary muscle tachycardia
Tachycardias were noted to arise from the base of the posterior papillary muscle and having a non reentrant mechanism. ECG showed a right bundle branch block pattern with superior axis QRS axis. The tachycardia was not inducible by programmed atrial or ventricular stimulation. In two patients who had sustained ventricular tachycardia, it could not be terminated by overdrive pacing nor could features of entrainment be demonstrated. Ablation was challenging and needed irrigated tip catheters to tackle recurrence in some of the seven cases reported by the authors.
- Yamada T, et al. Idiopathic focal ventricular arrhythmias originating from the anterior papillary muscle in the left ventricle. J Cardiovasc Electrophysiol. 2009;20:866-72.
- Doppalapudi H et al. Ventricular tachycardia originating from the posterior papillary muscle in the left ventricle: a distinct clinical syndrome. Circ Arrhythm Electrophysiol. 2008;1:23-9.