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Cardiac resynchronization therapy restores optimal atrioventricular mechanical timing in heart failure patients with ventricular conduction delay

Angelo Auricchio, MD, PhD^*,*, Jiang Ding, PhD, Julio C. Spinelli, PhD, Andrew P. Kramer, PhD, Rodney W. Salo, MSc, Walter Hoersch, BE, Bruce H. KenKnight, PhD, Helmut U. Klein, MD^* for the PATH-CHF Study Group¹

^* Division of Cardiology, University Hospital, Magdeburg, Germany
Guidant Corporation, St. Paul, MinnesotaUSA

View larger version (15K): [in a new window]   Figure 1 Example of systolic left ventricular (LV) pressure during pacing (a) and intrinsic condition (b), intrinsic LV electrogram (c) and intrinsic right atrial (RA) electrogram (d) recorded from one patient. Also shown here is the presystolic peak (AP) due to atrial contraction and the start of pressure development in the LV (LS), the latter obtained as the point that first attained a slope 10% of maximum rate of increase of LV pressure. The interval (APLS) between AP and LS is defined as atrioventricular mechanical latency (AVL). When the ventricle is pre-excited with pacing, the LS point moves to the left, as shown here in curve a. To obtain the LS point in paced condition, the pressure curves in pacing and intrinsic condition are aligned at the right atrium electrical activation (RA). Thereafter, the difference between the two curves is obtained. The LS is the first point on the difference curve at which the slope is 10% of the maximum slope.

View larger version (52K): [in a new window]   Figure 2 The average aortic pulse pressure (PP), maximum rate of increase of left ventricular pressure (dP/dtmax) and left ventricular (LV) end-diastolic pressure (LVEDP) obtained during LV (left) and right ventricular (RV) (right) stimulation at each tested atrioventricular (AV) delay and at baseline (i.e., 100%) for the population, the responder subgroup and the nonresponder subgroup. Actual AV delays were normalized to baseline intrinsic AV interval (AVI) to simultaneously represent both the effect of short AVIs and pre-excitation present in the individual patients.

View larger version (38K): [in a new window]   Figure 3 (A) Relationship between aortic pulse pressure (PP) and atrioventricular mechanical latency (AVL) during left ventricle (LV) stimulation in the responder subgroup. Measurements are shown for all 19 patients with measurable and stable presystolic peaks. Pulse pressure changes are normalized to the maximum PP increases in each patient. Note that the AVL was calculated not only at five individual paced atrioventricular (AV) delays but also at the interpolated optimal AV delay for PP. The interpolation was based on a fourth order polynomial fit to the response curve. (B) Distribution of AVL values that corresponded to maximum increase in PP during LV stimulation in A. Each bin represents a 10 ms range of AVL values, and the number under each bin is the center value of that bin. (C) Same as A for 10 nonresponder patients. (D) Same as B for the nonresponder subgroup.

View larger version (16K): [in a new window]   Figure 4 Correlation of time from sensed activation in the right atrium (RA) to the peak of the atrial contraction as seen in the left ventricular (LV) pressure (RA-AP) and time from RA sense to the start of LV contraction (RA-LS) intervals that were calculated at the maximum aortic pulse pressure (PP) (A) and maximum rate of increase of LV pressure (dP/dtmax) (B). The difference between the RA-LS and RA-AP intervals is the atrioventricular mechanical latency (AVL). The identity line (dashed line) indicates an AVL of 0 ms. Points below the identity line occur when the onset of LV systolic pressure precedes the atrial systolic peak. Measurements are combined from patients with a measurable and stable presystolic peak and with maximum stimulation-induced PP and dP/dtmax increments of at least 5%. Stimulation chamber is identified in the legend. The linear regression was applied to all data points in each plot, and the regression equation and the correlation coefficient were displayed accordingly. BV = biventricular; RV = right ventricle/ventricular.