Left ventricular dyssynchrony

Pastore G, Noventa F, Piovesana PG et al (2008) Left ventricular dyssynchrony resulting from right ventricular apical pacing. Relevance of baseline assessment. Pacing Clin Electrophysiol 31 1456-1462... 

Bleeker GB, Schalij MJ, Molhoek SG, Verwey HF, Holman ER, Boersma E, Steendijk P, Van Der Wall EE, Bax JJ. Relationship between QRS duration and left ventricular dyssynchrony in patients with end-stage heart failure. J Cardiovasc Electrophysiol 2004 15 544-9. 

Bax JJ, Bleeker GB, Marwick TH, Molhoek SG, Boersma E, Steendijk P, van der Wall EE, SchaUj MJ. Left ventricular dyssynchrony predicts response and prognosis after cardiac resynchronization therapy. J Am CoU Cardiol 2004 44 1834-40. 

Badhwar N, Viswanathan M, O Connell JW, De Marco T, Schreck C, Lee BK, Tseng ZH, Lee RL, Olgin JE, Botviniek EH. Novel scintigraphic parameters to assess left ventricular dyssynchrony predict clinical response in heart failure patients requiring cardiac resynchronization therapy (abstract). J Nuc Med. 2006 47 (Supplement 1) 1P. 

Tops et al. recently reported on the development of left ventricular dyssyn-chrony and heart failure symptoms during long term right ventricular pacing following AV junction ablation in 55 patients with preserved systolic function at the time of ablation (59). Patients were followed for 3.8 1.7 years. During follow-up, 27 patients (49%) developed left ventricular dyssynchrony and worsened heart failure symptoms. The New York Heart Association functional class increased from 1.8 0.6 to 2.2 0.7, p < 0.05. The left ventricular ejection... 

Intraventricular conduction delay often leads to late activation of the left ventricular free wall with significant mechanical consequences. The mechanical consequences of abnormal electrical activation of the heart have long been recognized [58, 60, 86]. These include dyssynchrony between the atria. 

Echo has been used to assess aU levels of mechanical dyssynchrony dys-synchrony between the atrium and the ventricle, interventricular dyssynchrony, and intraventricular dyssynchrony. Echo Doppler imaging at the level of the mitral valve inflow shows the effects of a long AV interval (fused E and A waves with diastolic mitral regurgitation), short AV interval (truncation of A wave with loss of atrial kick), and optimal AV interval (aortic systolic flow starts at the end of A wave) (5,31). This is illustrated in Fig. 11.4. Pulsed-wave Doppler echocardiography has been used to evaluate interventricular dyssynchrony that is defined as the time difference between right and left ventricular pre-ejection intervals. This is usually measured from the onset of the QRS complex on the EKG (that correlates with the end of diastole) to the onset of the aortic and pulmonary ejection. Delayed aortic ejection time (>40-50ms) has been used as a marker of interventricular dyssynchrony that improves with CRT (32-34). 

Fig. 11.8 Stepwise algorithm for management of heart failure patients who are nonresponders to CRT. AV = atrioventricular CXR = chest X-ray EKG = electrocardiogram Htx = heart transplant LV = left ventricular LVAD = left ventricular assist device MR = mitral regurgitation RV = right ventricular VV = interventricular. Cardiac ischemia is evaluated in patients with ischemic cardiomyopathy. Evidence of dyssynchrony includes septal to posterior wall motion delay > 130ms, intraventricular mechanical delay >40ms, and tissue Doppler imaging > 65 ms. (Reproduced witih permission from Aranda JM, Woo GW, Schofield RS, et al. J Am Coll Cardiol 2005 46 2193-8.)...

Kapetanakis S, Kearney MT, Siva A, Gall N, Cooklin M, Monaghan MJ. Real-time three-dimensional echocardiography a novel technique to quantify global left ventricular mechanical dyssynchrony. Circulation 2005 112 992-1000. 

Disordered electrical and mechanical ventricular activation can compromise cardiac function. Pacing technology has been nsed to att pt to correct the inter- and intraventricular conduction in an effort to optimize cardiac performance. The earliest attempts were performed during surgery when epicardial leads were placed over the lateral left ventricle free wall. Later, the coronary sinus was utilized to activate the left ventricle. Cardiac-resynchronization therapy (CRT) for treatment of patients with congestive heart failure and ventricular dyssynchrony can have a remarkable beneficial effect. Use of this technology continues to evolve. 

The Cardiac Resynchronization in Heart Failure (CARE-HF) evaluated 813 patients with New York Heart Association Functional Class III or TV heart failure due to left ventricular systolic dysfunction and cardiac dyssynchrony (QRS interval > 120 ms) who were receiving standard pharmacologic therapy. Patients were randomly assigned to receive medical therapy alone or with cardiac resynchronization. The primary end point (time to death from any cause or an unplanned hospitalization for a major cardiovascular event) was reached by 159 patients in the cardiac-resynchronization group, as compared with 224 patients in the medical-therapy group (39 versus. 55% hazard ratio = 0.63 95% Cl 0.51-0.77 p < 0.001). There were 82 deaths in the cardiac-resynchronization group, as compared with 120 in the medical-therapy group (20 versus 30% hazard ratio = 0.64 95% Cl 0.48-0.85 P < 0.002) (194,195). 

Management of a Biventricular Device. It has been estimated that up to 38% of patients with moderate to severe congestive heart failure due to left ventricular systolic dysfunction have intraventricular conduction delays with wide QRS complexes and ventricular dyssynchrony (79). Cardiac resynchronization therapy using a biventricular pacemaker is now a Class I indication therapy for systolic heart failure in patients with a QRS complex > 120 ms and left ventricular ejection fraction < 35% (80). Although cardiac resynchronization therapy decreases heart failure hospitalizations (81,82), as the overall number of patients with biventricular pacemakers and ICDs increase, more critical care patients will present with implanted biventricular devices, and familiarity with the management of these devices will become increasingly important. 

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