Left ventricular lead electrical delay predicts response to cardiac resynchronization therapy
ABSTRACT Intracardiac electrograms can be used to guide left ventricular (LV) lead placement during implantation of cardiac resynchronization therapy (CRT) devices. Although attempts often are made to ensure that the LV lead is positioned at a site of maximal electrical delay, information on whether this is useful in predicting the acute hemodynamic response and long-term clinical outcome to CRT is limited.
The purpose of this study was to assess the ability of intracardiac (electrogram) measurements made during LV lead placement in patients undergoing CRT for predicting acute hemodynamic response and long-term clinical outcome to CRT.
Seventy-one subjects with standard indications for CRT underwent electrogram measurements and echocardiograms performed in the acute phase of this study. The LV lead electrical delay was measured intraoperatively from the onset of the surface ECG QRS complex to the onset of the sensed electrogram on the LV lead, as a percentage of the baseline QRS interval. Echocardiographic assessment of the hemodynamic response to CRT was measured as an intra-individual percentage change in dP/dt over baseline (DeltadP/dt, derived from the mitral regurgitation Doppler profile) with CRT on and off. dP/dt was measurable in 48 subjects, and acute responders to CRT were defined as those with DeltadP/dt >or=25%. Long-term response was measured as a combined endpoint of hospitalization for heart failure and/or all cause mortality at 12 months. Time to the primary endpoint was estimated by the Kaplan-Meier method, with comparisons made using the log rank test.
LV lead electrical delay correlated weakly with DeltadP/dt of the combined group (n = 48, r = 0.311, P = .029) but was strongly correlated with DeltadP/dt in the nonischemic subgroup (n = 20, r = 0.48, P = .027). LV lead electrical delay (%) was significantly longer in acute responders (69.6 +/- 23.9 vs 31.95 +/- 11.57, P = .002) among patients with nonischemic cardiomyopathy. A reduced LV lead electrical delay (<50% of the QRS duration) was associated with worse clinical outcome within the entire cohort (hazard ratio: 2.7, 95% confidence interval: 1.17-6.68, P = .032) as well as when stratified into ischemic and nonischemic subgroups.
Measuring LV lead electrical delay is useful during CRT device implantation because it may help predict hemodynamic response and long-term clinical outcome.
- SourceAvailable from: Emanuele Bertaglia
International journal of cardiology 01/2014; 172(2). DOI:10.1016/j.ijcard.2013.12.206 · 6.18 Impact Factor
- "presence of scarring) may impact the electrical activation pattern and explain our findings. A long electrical delay may represent either delayed overall electrical activation of that segment or slow conduction through a region of LV scar  . Our findings seem to suggest that a large variability in LV activation exists among CRT candidates, although the conventional lateral or postero-lateral LV segments might be preferred for lead positioning, as they are generally areas of late activation. "
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ABSTRACT: Several Sn-Ag-Cu lead-free solders and two kinds of metallic substrates, Cu and Cu/Ni/Au, were selected to explore the effect of microelements (Ni and Ge) on the interfacial reaction between solder and substrates. When solders reacted with Cu substrate, the thickness of the interfacial intermetallics of the Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge (in wt%) solder is several times as that of the Sn-3.5Ag-0.7Cu solder. Besides, the addition of microelements would transfer the feature of interfacial intermetallics from pebble shape to worm shape. However, the negligible difference in XRD data of these two alloys suggests that both interfacial intermetallics have the same crystal structure. The major interfacial intermetallic formed with Sn-3.5Ag-0.7Cu solder is Cu<sub>6</sub>Sn<sub>5</sub>, while it is (Cu<sub>x</sub>, Ni<sub>1-x</sub>)<sub>6</sub>Sn<sub>5</sub> with the solder containing Ni and Ge. The results of Electron Probe Microanalyzer (EPMA) investigation show that the aggregation of Ni in the interfacial intermetallics affects the interfacial reaction rate and the morphology of interfacial intermetallics. On the other hand, the features of the interfacial layer formed with a Cu/Ni/Au substrate are similar for the Sn-3.2Ag-0.5Cu and Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge solders. However, Ni and Ge enhance the shear strength of BGA solder ball attachment. The results of the cross section investigation indicate that the interfacial intermetallics were composed of coarse (Cu<sub>y</sub>, Ni<sub>1-y</sub>)<sub>6</sub>Sn<sub>5</sub> and fine uniformly dispersed Ni<sub>3</sub>Sn<sub>4</sub>.Electronic Materials and Packaging, 2002. Proceedings of the 4th International Symposium on; 01/2003
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