Cardiac resynchronization therapy defibrillator

The cardiac resynchronization therapy defibrillator device (CRT-D) provides the same pacing and defibrillation functions as an ICD, but can also pace the left ventricle for heart failure patients. 

Fig. 18.36 Posteroanterior chest radiograph obtained after the prior device was upgraded to a cardiac resynchronization therapy defibrillator system. During the course of the upgrade, the central venous circulation was perforated, and when dye was injected to determine the position of the sheath, the contrast material was seen in the mediastinum.

However, the long-term effects of cardiac resynchronization therapy (CRT) on morbidity and mortality were not known. Two clinical trials have established the morbidity and mortality effects of CRT. The COMPANION trial was a three armed trial, testing optimal medical therapy (OPT) against OPT plus CRT by a pacemaker or a OPT plus CRT by an implantable cardioverter-defibrillator (CRT-D) [118]. In this study, patients were enrolled prior to... 

Bristow MR, Saxon LA, Boehmer J, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure, [see comment]. N. Engl. J. Med. 2004 350 2140-50. 

Recent studies demonstrate that cardiac resynchronization therapy (CRT) offers a promising approach to selected patients with chronic heart failure. Delayed electrical activation of the left ventricle, characterized on the ECG by a QRS duration that exceeds 120 ms, occurs in approximately one-third of patients with moderate to severe systolic heart failure. Since the left and right ventricles normally activate simultaneously, this delay results in asynchronous contraction of the left and right ventricles, which contributes to the hemodynamic abnormalities of this disorder. Implantation of a speciahzed biventricular pacemaker to restore synchronous activation of the ventricles can improve ventricular contraction and hemodynamics. Recent trials show improvements in exercise capacity, NYHA classification, quality of life, hemodynamic function, and hospitalizations. A device that combined CRT with an implantable cardioverter-defibrillator (ICD) improved survival in addition to functional status. CRT is currently indicated only in NYHA class ni-IV patients receiving optimal medical therapy (ACE inhibitors, diuretics, -blockers, and digoxin) and... 

FIGURE 1.5 Summary of evidence supporting defibrillator implantation as stratified by ejection fraction and heart failure class in patients with ischemic cardiomyopathy (A) and nonischemic cardiomyopathy (B). For details of COMPANION trial, see Chapter 5. (CRT, cardiac resynchronization therapy EPS, electrophysiology study NYHA,New York Heart Association.)... 

Wilkoff BL, Hess M, Young J, Abraham WT. Differences in tachyarrhythmia detection and implantable cardioverter defibrillator therapy by primary or secondary prevention indication in cardiac resynchronization therapy patients. J Cardiovasc Electrophysiol 2004 15 1002-9. 

MADIT-CRT Automatic Defibrillator Implantation With Cardiac Resynchronization Therapy, ClinicalTrials.gov, http // www.clinicaltrials.gov/ct2/show/NCT00180271, accessed January 22,2008. 

Boriani G, Muller CP, Seidl KH, et al. Randomized comparison of simultaneous biventricular stimulation versus optimized interventricular delay in cardiac resynchronization therapy. The Resynchronization for the HemodYnamic Treatment for Heart Failure Management II implantable cardioverter defibrillator (RHYTHM IIICD) study. Am Heart J 2006 151 1050-8. 

There are three implantable devices used today to treat cardiac arrhythmias - the pacemaker, the implantable cardioverter defibrillator (ICD), and the cardiac resynchronization therapy (CRT) devices for heart failure patients. 

Moss AJ, Brown MW, Cannom DS, Daubert JP, Estes M, Poster E, Greenberg HM, Hall WJ, Higgins SL, Klein H, Pfeffer M, Wilber D, Zareba W. Multicenter automatic defibrillator implantation trial-cardiac resynchronization therapy (MADIT-CRT) design and clinical protocol. Ann Noninvasive Electtocardiol 2005 10 34-43. 

CRT, cardiac resynchronization therapy ICD, implantable cardioverter-defibrillator PA, posteroanterior... 

An increasing number of patients present for vascular access surgery carrying a CIED (e.g. internal pacemaker, defibrillator ICD, or cardiac resynchronization therapy) [14]. In these patients, the surgeon needs to brief the team ahead of time about the use of electrocautery. If monopolar cautery is needed, the pathway of the cautery current should be directed far away from the CIED, and the device should be reprogrammed or deactivated temporarily. Depending on the device and indication, the pacemaker function maybe adjusted to a reasonable rate and mode of action [15]. 

CRT reduces symptoms of CHF and improves cardiac performance in patients with moderate-to-severely symptomatic heart failure, severe left ventricular systolic dysfunction, normal sinus rhythm and a wide QRS complex. Resynchronization therapy significantly reduces hospitalizations in these patients and is highly cost-effective. Perhaps most important, resynchronization therapy for heart failure improves survival for these patients, particularly when employed in conjunction with an implantable defibrillator. However, randomized clinical trials show that a substantial minority of patients are clinical nonresponders. Therefore, critical questions remain with respect to identifying appropriate candidates for CRT, optimal device programming, and left ventricular lead placement. 

Byrd CL (2007) Managing device-related complications and transvenous lead extractions. In Ellenbogen KA, Kay GN, Wilkoff BL, Lau CP (eds.) Clinical cardiac pacing, defibrillation and resynchronization therapy (3rd edn) Saunders, Philadelphia, pp 855-930... 

The CARE-HF (Cardiac Resynchronization-Heart Failure) study was designed specifically to evaluate the effects of CRT on morbidity and mortality (1). This trial was started in January 2001 and was published in April 2005. Eight hundred nineteen patients with EF <35% and evidence dyssyn-chrony were randomized to optimal medical therapy or CRT. Dyssynchrony was defined as either a QRS duration > 150 ms or a QRS duration of 120-149 ms with echocardiographic evidence of dyssynchrony. In the CRT group, there was a 37% risk reduction (p < 0.001) in the primary endpoint, which was a composite of death from any canse or unplanned hospitalization for a major cardiac event (Fig. 11.3). In terms of all-cause mortality (secondary endpoint), there was a 36% risk reduction (p < 0.002) in the CRT group compared to optimal medical therapy. This study went beyond COMPANION by showing that CRT alone, even without the defibrillator, could improve survival. 

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