Having received European approval in September, St. Jude Medical now announced FDA clearance of its Unify Quadra cardiac resynchronization therapy defibrillator (CRT-D) and the matching Quartet Left Ventricular Quadripolar Pacing Lead. The lead features four electrodes and the CRT-D is able to take advantage of them by providing up to ten different pacing configurations.
Because the electrodes cover a greater area, precise placement of the lead is less critical as adjustments of the electrical signal can be made via software. Like many other implantable devices from St. Jude, the Unify Quadra can wirelessly interface with the Merlin.net system for reporting both on the health of the patient and the status of the device.
The Quartet lead – used as part of the Unify Quadra system – features four electrodes spaced over 4.7 centimeters, enabling up to 10 pacing configurations. Multiple pacing configurations allow the physician to implant the lead in the most stable position without making trade-offs in electrical performance. This includes pacing closer to the base of the left ventricle, which recent studies associate with better patient outcomes and which may be more difficult with traditional bipolar leads. The quadripolar pacing electrodes also provide physicians more options to optimize CRT performance, such as pacing around scar tissue in the heart and avoiding the most common pacing complications. The many benefits conferred from the Quartet lead’s unconventional pacing have been demonstrated by implanters around the world and reported in a number of published studies.
Common pacing complications that can occur in patients implanted with a CRT system include high pacing thresholds and unintentional phrenic nerve or diaphragmatic stimulation. Patients with high pacing thresholds require significantly higher energy to pace the heart; this may reduce the device’s battery life requiring patients to have more surgeries to replace devices or cause pacing to be ineffective. Phrenic nerve and diaphragmatic stimulation occur when the electrical output from a device inadvertently activates the diaphragm muscle (either directly or via the phrenic nerve), causing patients to hiccup with the delivery of the pacing stimuli. In particular, phrenic nerve and diaphragmatic stimulation may be body-position sensitive and not evident at the time of the implantation procedure, while the patient is lying on their back. Both high pacing thresholds and phrenic nerve or diaphragmatic stimulation are often due to the location of the pacing lead electrode and with limited pacing options, may require that the lead be repositioned surgically or CRT be disabled.