Circulation: Arrhythmia and Electrophysiology February 2019 Issue

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Dr Paul Wong: Welcome to the monthly podcast on the beat for Circulation: Arrhythmia and Electrophysiology. I'm Dr Paul Wong, Editor-in Chief with some of the key highlights from this month's issue.

This month's issue is dedicated to a new exciting topic, His bundle pacing. His bundle pacing is designed to achieve a more physiological human dynamic response than right ventricular pacing alone, which may be needed in patients with AV conduction abnormalities. In our first paper, Marek Jastrzebski and associates examined whether program stimulation may be used to distinguish nonselective His bundle capture from right ventricular myocardial capture. Premature beats were introduced at 10 millisecond steps during intrinsic rhythm, and also after a drive train of 600 milli seconds. The longest coupling interval that resulted in an abrupt change in the QRS morphology was considered equal to the effective refractory period of the His bundle or right ventricular myocardium.

Program His bundle pacing was performed from 50 different sites in 32 patients. In 34 out of 36 cases of nonselective His bundle pacing, the right ventricular myocardial effective refractory period was shorter than the His bundle effective a refractory period. 271 milliseconds versus 353 milliseconds, P less than 0.0001. Program His bundle pacing using a drive train typically resulted in an abrupt change of the QRS morphology. From nonselective His bundle to right ventricular myocardial QRS 34 out of 36 cases, or to selective His bundle QRS in two out of 36 cases. Program His bundle pacing deliver during native conduction resulted in obtaining selective His bundle QRS in 20 out of 34 patients, and right ventricular myocardial QRS in 14 out of 34 of the nonselective His bundle cases.

In right ventricular myocardial only pacing cases, so-called false nonselective His bundle pacing, and equals 14. Such responses were not observed. The QRS morphology remained stable. Therefore His bundle pacing correctly diagnosed, using programs stimulation, all nonselective His bundle cases in all right ventricular myocardial pacing cases.

In our next paper Aditya Saini and associates sought to determine whether the device electric cam can be used to differentiate between selective, nonselective His bundle pacing, and right ventricular septal capture. In 148 consecutive patients, His bundle pacing was performed. The near field ventricular electrogram morphology, the near field ventricular electrogram time to peak and the far field ventricular electrogram QRS duration were recorded while pacing the His bundle was simultaneous 12 lead ECG rhythm strips. The mean baseline QRS duration was 108 milliseconds, with QRS duration greater than 120 milliseconds in 57 or 39% of patients, including 27 with right bundle branch block, 18 with left bundle branch block, and 12 with an IVCD.

Selective His bundle pacing was noted in 54 or 36% of patients. A positive near field ventricular electrogram time to peak, and a near field ventricular electrogram time to peak of greater than 40 milliseconds were highly sensitive, 94% and 93% respectively, and specific 90% and 94% for selective His bundle pacing, irrespective of baseline QRS duration. All three parameters including positive near field ventricular electrogram time to peak, the near field ventricular electrogram time to peak greater than 40 milliseconds, and far field ventricular electrogram QRS duration less than 120 milliseconds had high predictive negative predictive value, 97%, 95%, and 92%. Therefore, a novel device-based algorithm for a selective His bundle pacing was proposed.

Electrogram transitions correlated with ECG transitions during threshold testing, and can accurately predict and differentiate between selective His bundle pacing, nonselective His bundle pacing, and right ventricular septal pacing with a cumulative positive predictive value of 91% and 100% in patients with a baseline QRS duration of less than 120 milliseconds.

In the next paper, Pugazhendhi Vijayaraman and associates examined whether Cardiac Resynchronization Therapy could be optimized by sequential His bundle pacing followed by left ventricular pacing, which the authors called His optimize CRT or hot CRT. Hot CRT was successfully achieved in 25 of 27 patients. The QRS duration and baseline was 183 milliseconds, and significantly narrowed to 162 milliseconds with biventricular pacing, to 151 milli seconds during His bundle pacing, and further to 120 milliseconds during hot CRT pacing, P less than 0.0001. During a mean follow-up of 14 months, left ventricular ejection fraction improved from 24 to 38%, P less than 0.0001, and New York Heart Association Functional Class changed from 3.3 to 2.04. 21 out of the 25 patients, or 84% were clinical responders, while 23 of 25, 92% showed echocardiographic response.

In our next paper, Parikshit Sharma and associates compared permanent His bundle pacing using three-dimensional electro anatomic mapping in low fluoroscopy in 10 patients, and compared the outcomes with conventional fluoroscopy guided His bundle pacing implants in 20 patients. His bundle pacing was successful in nine out of 10 patients using electro anatomic mapping, and 100% successful in the conventional patients. The mean His bundled fluoroscopy time was lower in electro anatomic mapping group, 0.2 minutes compared to eight minutes in the conventional group, P equals 0.002. The His bundle capture threshold was lower in the electro anatomic mapping group, 0.7 at one millisecond compared to the conventional group, 1.15 at one millisecond, P equals 0.04. There were no procedure related complications or lead dislodgements in either group.

In our next paper, Michael Orlov and associates describe a new technique in which pacing leads for permanent His bundle pacing were connected to electro anatomical mapping in 28 patients. The selective and nonselective His bundle capture sites were tagged. The His bundle cloud was 360 millimeters squared, and the lead was successfully deployed in 25 patients in the threshold of the His bundle pacing, and implant was 1.5 volts at 1.5 milli seconds.

In our final paper, Haran Burri and associates provide practical recommendations for programming pacemakers with His bundle pacing in order to deliver optimal therapy and ensure patient's safety. The authors discuss the important role of electrocardiographic analysis of His bundle capture. They also advise that ventricular capture management should be programmed inactive because of the absence of an evoked potential. The authors discuss the option of placing the His bundle electrode in the left and trigger a report of a cardiac resynchronization therapy pacemaker.

The readers will find this overview of programming His bundle pacing very informative. In this issue, we also have a very special year-end review, which highlights many of the top discoveries in our field. You will not want to miss it.

Okay. That's it for this month. We hope that you'll find the journal to be the go to place for everyone interested in the field. See you next time.

This program is copyright American Heart Association, 2019.

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