Case Studies

Introduction

A 91-year-old man was admitted with acute decompensated heart failure and renal insufficiency with a baseline creatinine of 1.8 mg/dl. The patient had a history of chronic heart failure with ejection fraction (EF) of 30%, atrial fibrillation, ventricular tachycardia, sick sinus syndrome, status post biventricular pacemaker insertion and hypertension.

The patient’s medications included: furosemide, aspirin, clopidogrel, amiodarone, Carvedilol, hydralazine and Simvastatin.

The patient was treated with Nesiritide and furosamide. Five days following his admission, he was transferred to the CCU because his condition did not improve. In the CCU he was treated with dobutamine at 6 mcg/kg/min. However, no clinical improvement was observed and he continued to experience dyspnea and progressive renal dysfunction (creatinine increased to 3.1 mg/dl).

At this stage it was decided to optimize his cardiac resynchronization therapy (CRT) device guided by NICOM measurements of cardiac output.

Cardiac Resynchronization Therapy (CRT) is a pacemaker based treatment for patients with advanced heart failure (e.g. NYHA Class III symptoms) with ejection fraction less than 35% who also have dyssynchronous activation of the muscle in different parts of the heart. CRT aims to restore synchrony of contraction, improve chamber contractility and thus improve quality of life, exercise tolerance and prolong life. This is accomplished by implantation of a pacemaker that connects to the heart with three electrodes: one in the right atrium (RA), one in the right ventricle (RV) and one placed via the coronary sinus and epicardial coronary veins on the left ventricular (LV) free wall. Once an atrial activation is detected, pacing signals are delivered to the RV and LV electrodes with the goal of activating all of the LV muscle as simultaneously as possible.

CRT devices have two important parameters that can be adjusted to optimize the clinical effectiveness of this therapy: the AV delay and the VV delay. The AV delay is the delay between the time when the atrial activation is detected and the time the RV pacing impulse is delivered. The VV delay is the time delay between RV and LV pacing impulse delivery.

Optimization of AV and VV delay settings may reduce the rate of non-responders and enhance response in those patients that do respond to CRT. Currently the most commonly used method for CRT optimization is traditional Doppler echocardiography. The NICOM provides a more user friendly and less time consuming method for CRT optimization.

CRT optimization with the NICOM

The patient is connected to the NICOM and once a steady cardiac output reading is attained, different AV and VV settings are tested while cardiac output is monitored continuously monitored. The goal is to determine the values of AV and VV intervals that provide the highest cardiac output. At baseline, the patient’s stroke volume was 54 ml/beat with a corresponding cardiac index (CI) of 2.25 l/min/m². After testing different VV settings (see Table 1) a value of 20ms was deemed to provide the best results, with a stroke volume of 78.7 ml/beat and a corresponding CI of 3.1 l/min/m². This corresponded to an increase of 38% compared to baseline.

Table 1.

Figure 1.

The following day a significant clinical improvement was observed with a gradual reduction in creatinine (Figure 1).

Four days later the patient was no longer dyspneic, he was on room air, was weaned off dobutamine and was transferred out of the CCU.

This case demonstrates the value of using NICOM for CRT optimization. There is a growing body of evidence demonstrating the clinical value of optimizing CRT parameter settings. This is particularly the case for long-term clinical benefits¹. This case illustrates that in a patient with chronic heart failure and a previously placed but never optimized CRT device who presents with an episode of significant decompensation, that optimization of the device can have a significant effect on cardiac output and short term clinical outcomes.

Despite the evidence, however, the need for a time consuming Doppler technique as well a highly trained echocardiographer and inter-user variation are limiting greater adoption of CRT optimization. NICOM-based CRT optimization offers a procedure that is user independent, easy to set up and simple to perform by a nurse or technician. ².

Cheetah Medical wishes to thank Magrieta Brandt RN, BSN, CCRN for contributing the case

¹Porciani MC, Dondina C, Macioce R, Demarchi G, Cappelli F, Lilli A et al. Temporal variation in optimal atrioventricular and interventricular delay during cardiac resynchronization therapy. J Card Fail 2006;12:715–9

Valzania C, Biffi M, Martignani C, Diemberger I, Bertini M, Ziacchi M et al. Cardiac resynchronization therapy: variations in echo-guided optimized atrioventricular and interventricular delays during follow-up. Echocardiography 2007;24:933–9

Zhang Q, Fung JW, Chan YS, Chan HC, Lin H, Chan S et al. The role of repeating optimization of atrioventricular interval during interim and long-term follow-up after cardiac resynchronization therapy. Int J Cardiol 2008;124:211–7

²Khan FZ, Virdee MS, Pugh PJ et al. Non-invasive cardiac output measurements based on bioreactance for optimization of atrio- and interventricular delays Europace. 2009 Dec;11(12):1666-74