Cardiac Resynchronization Therapy

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CRT

In the field of Cardiac Resynchronization Therapy (CRT) it is widely acknowledged that non-responder rates average at least 30%. Birnie et al contend that when using objective parameters of LV remodeling the non-responder rate is even higher; 40-50%.

There is further consensus that pacemaker lead placement is the most important determinant for improving CRT. According to Stevenson and Sweeney:

"Success of resynchronization is dependent on pacing from a site that changes the sequence of ventricular activation in a manner that translates to an improvement in cardiac performance. Ideally, pacing sites that produce the best hemodynamic effect would be selected". (Stevenson W.G., Sweeney M.O. Single Site Left Ventricular Pacing for Cardiac Resynchronization: Circulation. 2004;109:1741-4.)

This would imply that the best acute hemodynamic effect is a consequence of an instantaneous decrease in intraventricular dyssynchrony; the mechanism CRT is designed to tackle. Conversely a poorly selected site may induce an accute increase in intraventricular dyssynchrony and a subsequent decrease in cardiac performance ultimately leading to a (disadvantageous) remodeling of the left ventricle.

With the help of CD Leycom's Pressure-Volume catheter technique, the physician is able to determine the level of dyssynchrony and the‘hemodynamics' for each pacemaker lead position in real-time. The chronic effects of acute hemodynamic improvement during CRT is elegantly demonstrated by Steendijk et al.

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1	Cardiac resynchronization therapy for the causal treatment of heart failure with preserved ejection fraction: insight from a pressure-volume loop analysis. Penicka et al. Eur J Heart Fail. 2010 Apr 30
2	"Cardiac resynchronization therapy results in an improvement in short-term hemodynamic variables in patients with a QRS less than 120 ms related to both contractile improvement and relief of external constraint." [PV-data acquired] Williams et al. Short-Term Hemodynamic Effects of Cardiac Resynchronization Therapy in Patients With Heart Failure, a Narrow QRS Duration, and No Dyssynchrony. Circulation. 2009 Oct 27;120(17):1687-1694. Epub 2009 Oct 12.
3	"...Pressure-volume loop analysis during pacemaker/ICD implantations facilitates the determination of the optimal LV pacing site." Delnoy et al. Pressure-volume loop analysis during implantation of biventricular pacemaker/cardiac resynchronization therapy device to optimize right and left ventricular pacing sites. Eur Heart J.2009;30:797-804
4	”Echocardiographic dyssynchrony parameters have no place in denying potentially life-saving treatment or in exposing patients to unnecessary risks and draining health care resources” Hawkins NM, Petrie MC, Burgess MC, McMurray JJ. Selecting patients for Cardiac resynchronization Therapy. The fallacy of echocardiographic dyssynchrony. J Am Coll Cardiol 2009;53:1944-59
5	...Adding a second LV lead does not result in further improvement in acute hemodynamic response with respect to standard CRT when the single LV pacing site and atrioventricular interval are optimal" (research conducted with CD Leycom's PV-technology) Padeletti et al. Dual-site left ventricular cardiac resynchronization therapy. Am J Cardiol. 2008;102:1687-92.
6	”Given the modest sensitivity and specificity no single echocardiographic measure of dyssynchrony may be recommended to improve patient selection for CRT" Chung ES, Leon AR, Tavazzi L, et al. Results of the predictors of response to CRT (PROSPECT) trial. Circulation. 2008;117:2608-16
7	"Changes in systolic and diastolic function were both highly dependent on the LV stimulation site." de Cock et al. Effects of stimulation site on diastolic function in cardiac resynchronization therapy. Pacing Clin Electrophysiol. 2007;30 Suppl 1:S40-2.
8	...Acute His bundle pacing did not improve LV function compared with alternate site RV pacing and may be inferior to LV pacing. Padeletti et al. Accute effects of His bundle pacing versus left ventricular and right ventricular pacing on left ventricular function. Am J Cardiol. 2007;100:1556-60.
9	“Non-responder rate to CRT varies between 40-50% using objective parameters of LV remodeling. The extent of mechanical dyssynchrony and LV pacing site are considered critically important”. Birnie DH, ASL Tang. The problem of non-response to cardiac resynchroniztion therapy. Curr Opin Cardiol 2006;21:20-26.
10	Pressure-volume-dyssynchrony analysis demonstrated long-term benefits of CRT. Steendijk P, Tulner SA, Bax JJ, et al. Hemodynamic effects of Long-term cardiac resynchonization Therapy. Analysis by pressure-volume loops. Circulation. 2006; 113:1295-1304.
11	Pressure-volume-dyssynchrony analysis with CD Leyom's technology showed marked dependency on right ventricular pacing sites for optimal bi-ventricular pacing. Lieberman R, Padeletti L, Schreuder J, et al. Ventricular pacing lead location alters systemic Hemodynamics and left ventricular function in patients with and without reduced ejection fraction. J Amer Coll Cardiol 2006; 48:1634-16
12	Simultaneous BiV pacing acutely enhances both systolic and diastolic function over single-site RV or LV pacing in CHF patients with atrial fibrillation and AV block. Hay I, et al. Short-term effects of right-left heart sequential cardiac resynchronization in patients with heart failure, chronic atrial fibrillation, and atrioventricular nodal block. Circulation. 2004;110:3404-10.(Methodology included use of CD Leycom's pressure-volume technique)
13	Left ventricular pacing minimizes diastolic ventricular interaction, allowing improved preload-dependent systolic performance. Bleasdale RA, et al. Left ventricular pacing minimizes diastolic ventricular interaction, allowing improved preload-dependent systolic performance.Circulation. 2004;110:2395-400.(Methodology included use of pressure-volume technique)
14	Success of resynchronization is dependent on pacing from a site that changes the sequence of ventricular activation in a manner that translates to an improvement in cardiac performance. Ideally, pacing sites that produce the best hemodynamic effect.. Stevenson W.G., Sweeney M.O. Single Site Left Ventricular Pacing for Cardiac Resynchronization: Circulation. 2004;109:1741-4.
15	It will be useful if additional parameters can be developed that identify dyssynchrony in the human heart in a more sensitive and specific way, and potentially helpful if they are utilized to help place CRT leads in the future. Willerson JT, Kereiakis DJ. Cardiac resynchronization therapy: helpful now in selected patients with CHF. Circulation 2004;109:308-309.
16	Pressure-volume measurements enable assessment of systolic and diastolic left ventricular function and quantification of mechanical dyssynchrony in a continuous and on-line fashion. Steendijk P et al. Pressure-volume measurements by conductance catheter during cardiac resynchronization therapy. Eur Heart J 2004;6D:D35-D42.
17	Compared with RV pacing, LV based pacing significantly improved the indexes of LV function (end-systolic elastance) as was demonstrated by CD Leycom's pressure-volume technique. Simantirakis EN et al, J Am Coll Cardiol 2004;43:1013—8.
18	Pressure-volume loops measured with CD Leycom's technology offer real-time guidance for epicardial lead placement in CRT therapy. Dekker A, et al. Epicardial left ventricular lead placement for cardiac resynchronization therapy: Optimal pace site selection with pressure-volume loops. J Thorac Cardiovasc Surg 2004;127:1641-1647.

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