Device Therapy

JoAnn Green, MSN, RN, CCRN, Lakshmi Halasyamani MD, Connie Lewis MSN, ACNP, ANP

The importance of a multidisciplinary team in the treatment of HF cannot be over stated. Hospitalists must work with cardiologists to ensure that their patients receive appropriate pharmacological and device therapies to effectively manage heart failure. In addition to medical therapies, there are several device-based therapies that are used in patients with heart failure. The types and devices and indications for their use are listed below. These factors are additional issues that need to be addressed in the development of a specific intervention or may represent a specific target population.

The decision to undertake electrophysiological intervention must be made in the context of an individual patient’s functional status, prognosis, severity of underlying heart failure and co-morbid conditions. 

Devices considered for patients with heart failure include:

1. Implantable Cardioverter Defibrillators (ICDs)
2. Biventricular pacing/ cardiac resynchronization therapy (CRT)
3. Combination ICD/CRT devices
4. Ventricular Assist Devices (VADs)

Implantable Cardioverter Defibrillators (ICDs)

Primary prevention refers to ischemic and non ischemic patients who are at risk for sudden cardiac death (SCD). ICD therapy is recommended for primary prevention of SCD:

1. Patients with left ventricular ejection fraction < 35% and mild to moderate HF symptoms, NYHA class II or III, ischemic or non ischemic
2. Patients with LVEF less than or equal to 35% due to prior MI who are at least 40 days post-MI and are in NYHA functional Class II or III.
3. ICD therapy is indicated in patients with LV dysfunction due to prior MI who are at least 40 days post-MI, have an LVEF less than or equal to 30%, and are in NYHA functional Class I.
4. Consider for patients undergoing biventricular pacing/CRT device

Secondary prevention refers to patients that have survived a cardiac arrest due to VT or VF.

ICD placement is not recommended for patients with chronic, severe refractory HF when there is no reasonable expectation for improvement or in patients who are not expected to survive one year.

Biventricular Resynchronization Pacing

Biventricular resynchronization pacing is also known as cardiac resynchronization therapy (CRT).  Some patients with advanced HF have significant intra- or interventricular conduction delays that result in asynchronous contractions of the ventricles. The ventricular dyssynchrony is often seen as a wide QRS Complex (>120ms) with a left bundle branch block. Biventricular pacing studies have shown improvement in cardiac function.

CRT fires into the ventricles both at the same time resulting in a more efficient and forceful cardiac contraction and improved cardiac output. CRT works by placing a lead in the right ventricle and a second lead in the coronary sinus via a coronary vein over the left ventricle. When both leads fire at the same time it results in a re-synchronizing of the ventricles, and in patients with Stage C & D HF (NYHA Class III or IV) and wide QRS complex the use of CRT decreases mortality up to 24%.³

CRT is recommended for patients with:

1. Recommended for patients in sinus rhythm with QRS > 120ms and LVEF < 35% who have moderate to severe persistent symptoms despite optimal medical therapy.
2. Considered for patients with atrial fibrillation with QRS > 120ms and LVEF < 35% who have moderate to severe persistent symptoms despite optimal medical therapy.
3. Consider for ambulatory patients with NYHA class IV symptoms who are in sinus rhythm with QRS > 120ms
4. Consider for patients with NYHA class I symptoms with QRS > 150ms
5. Consider in patients with reduced LVEF who require chronic pacing and in whom it is expected will require frequent ventricular pacing

Combined ICD/CRT Therapy

Patients who are eligible for CRT may also be eligible for ICD placement.

Patients with HF receiving CRT along with an ICD have up to as much as a 43% reduction in mortality compared with drug therapy alone.

The HFSA 2010 Executive Summary and Guideline for Comprehensive HF Practice can be found in the Journal of Cardiac Failure Vo.16 No61, June 2010.

Ventricular Assist Devices (VADs) – Mechanical Circulatory Support (MCS)

A ventricular assist device (VAD) is a mechanical pump that can provide partial or total circulatory support when the natural heart, with optimal pharmacological therapy, is unable to maintain adequate circulation to perfuse vital organs. It is used to provide short-term hemodynamic support, as a "bridge-to-transplant" for those whose medical therapy has failed and are hospitalized with end-stage systolic heart failure, or as destination therapy.

References

1. Young, J. B., & Mills, R. M. (2004). Clinical management of heart failure (2nd ed.). West Islip, New York: Professional Communications, Inc.
2. Jessup M, Abraham WT, Chin MH, et al. 2009 Focused Update: ACCF/AHA Guidelines for the diagnosis and management of heart failure in the adult: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines.
3. Albert, N. M. Cardiac resynchronization therapy through biventricular pacing in patients with heart failure and ventricular dyssynchrony. Critical Care Nurse, Supplement June 2003; 23 (3):  2-13.
4. Wadas, T. M. The implantable hemodynamic monitoring system. Critical Care Nurse October 2005; 25 (5):  14-26.
5. Harding J. D. et al. Prolonged repolarization after ventricular assist device support is associated with arrhythmias in humans with congestive heart failure. Journal of Cardiac Failure 2005; 11 (3): 227-232
6. Lindenfield, J, Albert NM, et al Heart Failure Society of America 2010 Comprehensive Heart Failure Practice Guidelines.J Cardiac Failure. 2010;16:e194.