Implantable extravascular electrical stimulation lead having improved sensing and pacing capability

#The present application relates to electrical stimulation leads and, more particularly, electrical stimulation leads with improved sensing and/or pacing capability for use in extravascular applications.

#Malignant tachyarrhythmia, for example, ventricular fibrillation (VF), is an uncoordinated contraction of the cardiac muscle of the ventricles in the heart, and is the most commonly identified arrhythmia in cardiac arrest patients. If this arrhythmia continues for more than a few seconds, it may result in cardiogenic shock and cessation of effective blood circulation. As a consequence, sudden cardiac death (SCD) may result in a matter of minutes.

#In patients at high risk of ventricular fibrillation, the use of an implantable cardioverter-defibrillator (ICD) system has been shown to be beneficial at preventing SCD. An ICD system includes an ICD, which is a battery powered electrical stimulation device, that may include an electrical housing electrode (sometimes referred to as a can electrode), that is coupled to one or more electrical stimulation leads. The electrical stimulation leads may be placed within the heart, within vasculature near the heart (e.g., within the coronary sinus), attached to the outside surface of the heart (e.g., in the pericardium or epicardium), or implanted subcutaneously above the ribcage/sternum. If an arrhythmia is detected, the ICD may generate and deliver a pulse (e.g., cardioversion or defibrillation shock) via the electrical stimulation leads to shock the heart and restore its normal rhythm.

#FIGS. 1A and 1B are conceptual drawings illustrating various views of a patient implanted with an example extravascular implantable cardioverter-defibrillator (ICD) system.

#FIGS. 2A-2C are conceptual drawings illustrating various views of a patient implanted with an example extravascular ICD system in which a distal portion of the lead is implanted substernally.

#FIG. 3 is a drawing illustrating a distal portion of an example extravascular implantable medical electrical lead.

#FIGS. 1A and 1B are conceptual diagrams of an extravascular and/or extracardiac implantable cardioverter-defibrillator (ICD) system 10. ICD system 10 is subcutaneously implanted within a patient 12. FIG. 1A is a front view of ICD system 10 implanted within patient 12. FIG. 1B is a side view of ICD system 10 implanted within patient 12. ICD system 10 includes an ICD 14 connected to an extravascular and/or extracardiac electrical stimulation lead 16. FIGS. 1A and 1B are described in the context of an ICD system capable of providing defibrillation and/or cardioversion shocks and, in some instances, pacing pulses. However, the techniques of this disclosure may also be used in the context of other implantable medical devices configured to provide electrical stimulation pulses to stimulate other portions of the body of patient 12.

#ICD 14 may include a housing that forms a hermetic seal that protects components of ICD 14. The housing of ICD 14 may be formed of a conductive material, such as titanium or titanium alloy. The housing of ICD 14 may function as a housing electrode (sometimes referred to as a can electrode). In other instances, the housing of ICD 14 may include a plurality of electrodes on an outer portion of the housing. The can electrode and/or the plurality of electrodes on the outer portion of the housing may be coated with a material, such as titanium nitride. ICD 14 may also include a connector assembly (also referred to as a connector block or header) that includes electrical feedthroughs through which electrical connections are made between conductors extending within the body of lead 16 and electronic components included within the housing of ICD 14. As will be described in further detail herein, housing may house one or more processors, memories, transmitters, receivers, sensors, sensing circuitry, therapy circuitry, power sources and other appropriate components. The housing is configured to be implanted in a patient, such as patient 12. ICD 14 is implanted subcutaneously on the left side of patient 12 above the ribcage. ICD 14 may, in some instances, be implanted between the left posterior axillary line and the left anterior axillary line of patient 12. ICD 14 may, however, be implanted at other subcutaneous locations on patient 12 as described later.

#Lead 16 includes an elongated lead body having a proximal end that includes a connector (not shown) configured to be connected to ICD 14 and a distal portion that includes one or more electrodes. In the example illustrated in FIGS. 1A and 1B, the distal portion of lead 16 includes defibrillation electrode segments 24A and 24B, and pace/sense electrodes 28A, 28B, and 30. In some cases, defibrillation electrode segments 24A and 24B may together form a defibrillation electrode in that they are configured to be activated concurrently. Alternatively, defibrillation electrode segments 24A and 24B may form separate defibrillation electrodes in which case each of the electrodes 24A and 24B may be activated independently. In some instances, ICD 14 may include switching mechanisms to allow defibrillation electrode segments 24A and 24B coupled to separate conductors to be utilized as a single defibrillation electrode (e.g., activated concurrently to form a common cathode or anode) or as separate defibrillation electrodes, (e.g., activated individually). Electrode segments 24A and 24B are referred to as defibrillation electrode segments or defibrillation electrodes because they are utilized, individually or collectively, for delivering high voltage stimulation therapy (e.g., cardioversion or defibrillation shocks). However, electrode segments 24A and 24B may also be utilized to provide pacing functionality, sensing functionality or both pacing and sensing functionality in addition to or instead of high voltage stimulation therapy. In this sense, the use of the terms “defibrillation electrode segments” or “defibrillation electrode” should not be considered as limiting the electrode segments to use in only high voltage applications.