Bi-ventricular (“bi-vent”) pacing falls under the larger category of Cardiac Resynchronization Therapy (CRT) with the primary goal of resynchronizing both ventricles through simultaneous pacing. This can improve myocardial contractile function, reduce functional MR, and reverse cardiac remodeling associated with heart failure. The indications for bi-vent pacing have been changing regularly as more research is being done. Additionally, along with pacing the patient should also be on “guideline directed medical therapy” (GDMT) i.e. ACEI/ARB, beta-blocker, etc. A combined ICD/pacing device may also be placed as many patients receiving CRT qualify for an ICD as well.
According to the AHA recommendations, the current class I indication for NYHA Class II, III, and ambulatory IV individuals on GDMT are: EF <35%, LBBB, and QRS >150ms. This was updated to now include NYHA Class II patients, QRS duration increased from >120 to >150, and required a LBBB to be present.
Class IIa recommendations:
- NYHA Class III and ambulatory IV with non-LBBB, QRS >150ms, EF <35%
- NYHA Class II, III, and amb IV with LBBB, QRS 120-149ms, and EF <35%
- LV EF <35% and rate controlled afib with 100% ventricular pacing
- LV EF <35% and undergoing device implantation (new/replacing) with anticipated need for >40% ventricular pacing
- NYHA Class I (first time to include class I) with severe ischemic a cardiomyopathy EF <30%, LBBB, and QRS >150ms
- NYHA Class III and amb IV with non-LBBB, QRS 120-149, EF <35% NYHA Class II, III, and amb IV with non-LBBB, QRS >150 ms, and EF <35%
Class III (not recommended):
- Comorbidity (cardiac or non-cardiac) that is expected to limit good functional capacity to less than 1 year.
- NYHA patients with non-LBBB and QRS
Thus the primary shift in the recommendations has focused on a longer QRS prolongation, inclusions of additional NYHA classes, the presence of a LBBB versus another conduction delay (including RBBB). This may be due to limited patients having conduction delays other than LBBB in the studies.
From a practical perspective, patients often present to the operating room to have the biventricular pacemaker left ventricular (LV) lead placed as the lead may be difficult to insert via the transvenous approach. Normally, the left ventricular lead is placed under sedation transvenously via the coronary sinus and epicardial veins to the lateral wall of the left ventricle. When this approach is not possible, an anterior mini-thoracotomy may be used to place the LV lead.
For a patient who has a preexisting biventricular pacemaker and requires surgery, preoperative interrogation of the pacemaker is vital. These patients are mandatorily paced in both ventricles regardless of underlying native heart rhythm. Thus, any electromagnetic interference must be accounted for and the pacemaker should NOT be set to an alternative mode during surgery. For optimal cardiac function during the surgery and anesthetic, the biventricular pacing should continue.
Defined by: Nate Paulson, MD