Dynamic cardiomyoplasty: Long-term viability demonstrated by noninvasive on-line analysis of dynamic contractile characteristics of the human latissimus dorsi flap in Italian subjects

In dynamic cardiomyoplasty, load-independent measurements of cardiac function demonstrate a real improvement of heart energetics when preoperative and postoperative analyses are compared. In order to improve a patient's quality of life, latissimus dorsi (LD) muscle activation should optimally be delayed after the sensed QRS complex in order to avoid mitral valve regurgitation. To achieve greater systolic augmentation, it is essential to be able to monitor the LD flap contractile characteristics. Having a technique to noninvasively monitor the LD contraction 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 motion and heart sounds. Electrocardiographic (ECG), and heart tones are registered simultaneously with the pressure changes due to LD flap contraction and relaxation that are measured near the rib window using the probe normally used for recording an apicocardiogram. From the LD 'mechanogram,' we can determine: (1) LD activation threshold; (2) optimal synchronization delay between cardiac events and the actual contraction of the LD flap; (3) the duration of the full LD contraction-relaxation 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 resistant and slow contracting by the end of the conditioning period (within 2 months after the operation) and can remain viable at least up to 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 amount of impulses delivered per day. Optimal synchronization of the LD flap was determined in a subset of patients by catheterization and pressure-volume analysis. The optimal setting induces LD contraction during the systolic ejection phase, which can also be assessed noninvasively in the same subjects using echo Doppler imaging of the aortic outflow tract.