Method and apparatus for predicting recurring ventricular arrhythmias

#The present invention relates to a medical device and, more specifically, to a device and method for assessing cardiac autonomic tone and predicting the early recurrence of ventricular tachycardia or fibrillation and triggering an alert system for initiation of possible preventive measures.

#Ventricular tachycardia (VT) and ventricular fibrillation (VF) are serious, life-threatening forms of cardiac arrhythmias. Implantable medical devices, referred to as implantable cardioverter defibrillators or ICDs, are capable of automatically detecting arrhythmias and delivering anti-arrhythmia therapies. Delivering anti-tachycardia pacing therapies or high-energy shock therapies may terminate VT and VF. Ventricular tachycardia termination is typically referred to as “cardioversion.” Ventricular fibrillation termination is typically referred to as “defibrillation.”

#Nearly all of detected arrhythmias appropriately treated by an ICD do not result in death. However, some patients with ICDs do experience fatal arrhythmias. Compromised hemodynamic output during a VT or VF episode can render a patient unconscious resulting in related serious injuries or death. Patients may experience recurrent VT or VF and be subjected to repeated shock therapies, which cause great discomfort. Because of the serious consequences of VT and VF, it is desirable to predict the occurrence of VT and VF so that an ICD can be prepared to immediately deliver a therapy or take preventive measures to prevent the occurrence. Prediction of an imminent VT or VF episode also enables preventive medical treatments to be delivered.

#FIG. 1 is an illustration of an implantable cardiac stimulation device capable of pacemaking, cardioversion, and defibrillation and in communication with a patient's heart via three stimulation and sensing leads;

#FIG. 2 is a functional, block diagram of the implantable cardiac stimulation device shown in FIG. 1;

#FIG. 3 is a flow chart illustrating a method performed by the device shown in FIG. 2 for predicting an early VT or VF recurrence;

#As described above, the present invention is aimed at assessing cardiac autonomic tone and using this assessment, in conjunction with other parameters like myocardial ischemia, for predicting the recurrence of a ventricular tachycardia or fibrillation episode. The methods included in the present invention may be incorporated in an implantable or external monitoring device, or an implantable or external cardiac rhythm management device. In a preferred embodiment, the methods of the present invention are incorporated in an implantable cardiac device capable of monitoring the heart rhythm for detecting arrhythmias and delivering anti-arrhythmia therapies, such as the implantable cardioverter defibrillator (ICD) 10 shown in FIG. 1.

#ICD 10 is shown coupled to a patient's heart by way of three leads 6, 15, and 16. A connector block 12 receives the proximal end of a right ventricular lead 16, a right atrial lead 15 and a coronary sinus lead 6, used for positioning electrodes for sensing and stimulation in three or four heart chambers. In FIG. 1, the right ventricular lead 16 is positioned such that its distal end is in the right ventricle for sensing right ventricular cardiac signals and delivering pacing or shocking pulses in the right ventricle. For these purposes, right ventricular lead 16 is equipped with a ring electrode 24, an extendable helix electrode 26 mounted retractably within an electrode head 28, and a coil electrode 20, each of which are connected to an insulated conductor within the body of lead 16. The proximal end of the insulated conductors are coupled to corresponding connectors carried by bifurcated connector 14 at the proximal end of lead 16 for providing electrical connection to the ICD 10.

#The right atrial lead 15 is positioned such that its distal end is in the vicinity of the right atrium and the superior vena cava. Lead 15 is equipped with a ring electrode 21 and an extendable helix electrode 17, mounted retractably within electrode head 19, for sensing and pacing in the right atrium. Lead 15 is further equipped with a coil electrode 23 for delivering high-energy shock therapy. The ring electrode 21, the helix electrode 17 and the coil electrode 23 are each connected to an insulated conductor with the body of the right atrial lead 15. Each insulated conductor is coupled at its proximal end to a connector carried by bifurcated connector 13.