PracticeUpdate Cardiology Best of 2018

TOP STORIES 2018 7

The Benefits of His Bundle Pacing

By Douglas P. Zipes MD T ransvenous cardiac pacing began almost 60 years ago with the observation by Furman and Schwedel that stimula- tion of the right ventricular

(RV) endocardium produced ventricular con- traction. 1 For many years thereafter, RV apical lead placement represented the transvenous pacingmodel of choice. Attempts at His bundle pacing to create normal ventricular electrical systole were fragmentary and largely aban- doned because of lead placement difficulties. When a pacing-induced cardiomyopathy from the resultant LBBB during RV apical pacing became known, high septal and outflow RV pacing was attempted, mostly replaced by cardiac resynchronization therapy (CRT). CRT, although successful, is cumbersome by requir- ing a left ventricular lead, expensive, and has a higher complication rate than simple RV pacing. Fortunately, several groups re-investigated the concept of His bundle pacing, and pre- liminary findings indicate that it is feasible, practical, and beneficial. 2,3,4 The success of His bundle pacing represents the top 2018 story because it restores normal physiologic electrical ventricular depolarization with a sin- gle lead even in the presence of most bundle branch blocks, and it eliminates the need for left ventricular pacing and the potential for a pacing-induced cardiomyopathy. Further lead and electrode development will make His bundle pacing the optimal choice for ven- tricular pacing. I anticipate it will replace CRT. As such, it becomes a therapeutic paradigm shift in the world of pacing. References 1. Furman S, Schwedel JB. An intracardiac pacemaker for Stokes-Adams seizures. N Engl J Med 1959;261:943-948. 2. Huang W, Su L, Wu S, et al. Long-term outcomes of His bundle pacing in patients with heart failure with left bundle branch block. Heart 2018 Aug 9. doi:10.1136/heartjnl-2018-313415. [Epub ahead of print.] 3. Vijayaraman P, Chung MK, Dandamudi G, et al. His bundle pacing. J Am Coll Cardiol 2018;72(8):927-947 4. Ezzeddine FM, Dandamudi G. Updates on His bundle pacing: the road more traveled lately. Trends Cardiovasc Med 2018 Sep 9. doi:10.1016/j. tcm.2018.09.018. [Epub ahead of print.] www.practiceupdate.com/c/74883

are modest. In a therapeutic trial of, say, the new PCSK9-inhibitors, such as the FOURIER trial, 6 where 100% of the inter- vention group is initially on the drug while 0% are on the drug in the control group, a 38% reduction in non-fatal MI was seen. In SCOT-HEART, the abso- lute difference in aspirin and stain use was on the order of ~ 10%, with a larger relative risk reduction in MI than seen in FOURIER. Thus, the mechanism under- lying the striking reduction in MI risk in SCOT-HEART is unclear. The SCOT-HEART data are in contrast to those of the PROMISE trial, where, with over 2 years of follow-up, no difference in outcomes was observed. Although patients in both trials had CCTA-based management as one randomization arm, the difference in the trials was the comparator arm. In SCOT-Heart, the comparator was predominantly exer- cise ECG (only ~ 10% of patients had an imaging stress test, nuclear or echo), whereas in PROMISE, the comparator was predominantly stress imaging (only ~ 10% of patients had exercise ECG). One might interpret the totality of results from these two trials (as well as the more recent CRESCENT–II trial, comparing a “tiered” CT approach to exercise ECG) that there is now little role for exercise ECG in out-patients with suspected CAD, and that stress imaging or CCTA should lead to similar outcomes.

The SCOT-HEART trial joins the pantheon of randomized trials of diagnostic strate- gies for its novel findingof anassociationof initial CCTAwith reducedMI risk. The data reinforce a general message regarding the importance of aggressive preventive measureswhenCAD is suggested (by any test!), so that the testing results can drive management well beyond simply being used for diagnosis of CAD. References electrocardiography with or without myocardial perfusion single photon emission computed tomography in women with suspected coronary artery disease: results from the What Is the Optimal Method for Ischemia Evaluation in Women (WOMEN) trial. Circulation 2011;124(11):1239–1249. 2. Douglas PS, Hoffmann U, Patel MR, et al. Outcomes of anatomical versus functional testing for coronary artery disease. N Engl J Med 2015;372(14):1291-1300. 3. SCOT-HEART investigators. CT coronary angiography in patients with suspected angina due to coronary heart disease (SCOT-HEART): an open-label, parallel-group, multicentre trial. Lancet 2015;385(9985):2383-2391. 4. SCOT-HEART Investigators, Newby DE, Adamson PD, et al. Coronary CT angiography and 5-year risk of myocardial infarction. N Engl J Med 2018;379(10):924-933. 5. Hoffmann U, Udelson JE. Imaging coronary anatomy and reducing risk of myocardial infarction. N Engl J Med . 2018;379(10):977-978. 6. Sabatine MS, Giugliano RP, Keech AC, et al. Evolocumab and clinical outcomes in patients with cardiovascular disease. N Engl J Med 2017;376(18):1713-1722. www.practiceupdate.com/c/76418 1. Shaw LJ, Mieres JH, Hendel RH, et al. Comparative effectiveness of exercise

VOL. 3 • NO. 4 • 2018