Automatic Beat‐to‐Beat Left Heart AV Normalization:

Abstract

Programming the right heart AV interval to a normal value may cause a nonphysiological left heart AV due to interatrial and interventricular conduction delays, thus affecting cardiac performance. Since AV normalization at rest and exercise may be invalidated by pacing or sensing (mode) changes, the aim of this study was to (1) study the feasibility of a mode independent pacemaker (PM) algorithm for automatic beat-to-beat left AV normalization, (2) establish normal values for the time between mitral flow A wave (Af) and ventricular activation (Va), the AfVa interval, the mechanical surrogate of left AV, and (C) determine the range of values of the interatrial electromechanical delays (IAEMDs) and the effect of RA pacing. To pace with the proper right AV, the previously reported RV-paced interventricular electromechanical delay and the interatrial electromechanical delay, either P-sensed (IAEMDs) or atrial-paced (IAEMDp) are required inputs. Data were collected during diagnostic echo Doppler studies in 84 subjects divided in three groups: (1) control with narrow QRS and no structural heart disease (n = 33, age 50 +/- 21 years, 42% men); (2) patients in sinus rhythm with diverse cardiac pathologies except LBBB (n = 39, age 69 +/- 14 years, 56% men), and (3) DDD-paced patients (n = 12, mean age 71 +/- 6 years). Normal values of AfVa were established from the control group, while IAEMDs and IAEMDp and active atrial flow time (A-peak), in all subjects. The algorithm was tested by computer simulation under all possible modes with the following calculation: RAV = N + IAEMD - IVD, where RAV is the right AV, N is the desired normal AfVa value, IAEMD is either P-sensed or A-paced, and IVD is close to zero for intrinsic narrow QRS and biventricular pacing, or 79 ms for RV pacing. The results demonstrated (1) Normal (controls) AfVa: 85 +/- 15 ms (range 52-110 ms); (2) IAEMDs (All): 84 +/- 16 ms; (3) atrial pacing prolonged IAEMDs by 57 +/- 18 ms (from 93 +/- 15 to 150 +/- 25 ms, P < 0.0001); and (4) Computer simulation of rate and mode changes validated the normalization algorithm. An automatic, beat-to-beat left AV normalization algorithm to preserve a normal AfVa without a hemodynamic sensor is feasible. The normal value of AfVa is 85 +/- 15 ms.

Optimal Atrioventricular Delay in CRT Patients Can Be Approximated Using Surface Electrocardiography and Device Electrograms

“…The relation between P‐wave duration or interatrial conduction interval and optimal AV delay has been explained previously 25–27 . Optimal AV interval requires LV contraction to start soon after the completion of LA contraction.…”

“…The timing of the LA contraction is determined by LA electrical activation, which is reflected in the final portion of the P‐wave during normal sinus rhythm or right atrial (RA) pacing 26 . Similarly, LV contraction occurs at a certain delay after LV activation, which starts shortly after the biventricular pacing 25 . Therefore, the interval from the end of the P‐wave to the biventricular pacing pulse is more directly related to LA‐to‐LV timing compared with the device AV delay, which represents RA‐to‐LV timing.…”

Interatrial Conduction Correlates with Optimal Atrioventricular Timing in Cardiac Resynchronization Therapy Devices

“…Several patient‐specific factors, such as conduction between the right and left atria as well as electro‐mechanical coupling, are responsible for this difference 9–11 . The optimal device AV delay can be determined by either accounting for these factors 12 or, alternatively, by iterating through a number of device settings and evaluating cardiac function at each. Earlier publications have indicated that interatrial conduction time (IACT), defined as the delay between the activation of the right and left atria, may be an important determinant of the optimal AV delay 12,13 .…”

“…The optimal device AV delay can be determined by either accounting for these factors 12 or, alternatively, by iterating through a number of device settings and evaluating cardiac function at each. Earlier publications have indicated that interatrial conduction time (IACT), defined as the delay between the activation of the right and left atria, may be an important determinant of the optimal AV delay 12,13 . We have previously reported a positive correlation between IACT and optimal AV during atrial pacing 14 .…”

Group Purchasing Organizations: Optimizing Cardiac Device Selection, Therapy Delivery, and Fiscal Responsibility

“…Mode switching is another example of an over utilized algorithm that can have negative patient consequences. Mode switch studies have shown that inappropriate mode switching occurs anywhere from 9% to 38% of the time 42–56 . These occurrences can be especially detrimental to CRT patients where therapy delivery will be inappropriately withheld.…”