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)

ICDs prevent sudden cardiac death in a subset of patients with ischemic or non-ischemic heart failure (NYHA II- III).  Patients eligible for evaluation for prophylactic ICD placement include:

1. Patients who are on chronic optimal (ACC/AHA Guidelines) medical therapy  
2. Patients with ejection fraction </+ 30%
3. Patients with ejection fraction 31-35% may be considered

ICD placement is not recommended for patients with chronic, severe refractory HF when there is no reasonable expectation for improvement.

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 should be considered for patients with all of the following:

1. Sinus rhythm
2. Widened QRS (>/= 120ms)
3. Severe LV systolic dysfunction (LVEF </= 35% with LV dilation > 5.5 cm)
4. Persistent, moderate to severe HF (NYHA III) despite optimal medical therapy

CRT is not recommended for patients who are asymptomatic or have mild HF symptoms.

The routine use of dual (atrioventricular) (AV) chamber cardiac pacemakers for HF in the absence of symptomatic bradycardia or high grade AV block is not recommended. (HFSA)

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 2006 Executive Summary and Guideline for Comprehensive HF Practice can be found in the Journal of Cardiac Failure Vo.12 No.1, February 2006.

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. Hunt S. A., Abraham, W. T., et al. Diagnosis and management of chronic heart failure in the adult. American College of Cardiology and American Heart Association Pocket Guideline, August 2005.
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