DYNAMIC CARDIOMYOPLASTY - LONG-TERM VIABILITY DEMONSTRATED BY NONINVASIVE ONLINE ANALYSIS OF DYNAMIC CONTRACTILE CHARACTERISTICS OF THE HUMAN LATISSIMUS-DORSI FLAP IN ITALIAN SUBJECTS

In dynamic cardiomyoplasty, load-independent measurements of cardiac f unction demonstrate a real improvement of heart energetics when preope rative and postoperative analyses are compared. In order to improve a patient's quality of life, latissimus dorsi (LD) muscle activation sho uld optimally be delayed after the sensed QRS complex in order to avoi d mitral valve regurgitation. To achieve greater systolic augmentation , it is essential to be able to monitor the LD flap contractile charac teristics. Having a technique to noninvasively monitor the LD contract ion and relaxation would facilitate the evaluation of new stimulation regimes or other techniques for improving LD function. We developed a new method for noninvasive, bedside monitoring of LD function using a standard polygraph, previously used for monitoring cardiac apical moti on and heart sounds. Electrocardiographic (ECG), and heart tones are r egistered simultaneously with the pressure changes due to LD flap cont raction and relaxation that are measured near the rib window using the probe normally used for recording an apicocardiogram. From the LD ''m echanogram,'' we can determine: (1) LD activation threshold; (2) optim al synchronization delay between cardiac events and the actual contrac tion of the LD flap; (3) the duration of the full LD contraction-relax ation cycle; and (4) the dynamic contractile characteristics of the LD flap based on the determination of the tetanic fusion frequency. In a cohort of patients, we have shown that the LD flap becomes fatigue re sistant and slow contracting by the end of the conditioning period (wi thin 2 months after the operation) and can remain viable at least up t o 50 months (the longest patient follow-up in this series). The extent of fast-to-slow transformation of contractile characteristics of the LD flap can be related to the stimulation protocols used i.e., the amo unt of impulses delivered per day. Optimal synchronization of the LD f lap was determined in a subset of patients by catheterization and pres sure-volume analysis. The optimal setting induces LD contraction durin g the systolic ejection phase, which can also be assessed noninvasivel y in the same subjects using echo Doppler imaging of the aortic outflo w tract.