DEVELOPMENTAL DIFFERENCES IN CANINE CARDIAC SURGICAL SCARS

Sudden death and arrhythmias are significant problems in patients with various types of repaired congenital heart disease and have been asso ciated with increasing time after and older age at surgery. Arrhythmia s have been mapped clinically to areas of surgical scars in some patie nts, leading to the hypothesis that scar morphology changes with age. This study compared the morphology and histology of right ventriculoto my scars or right atriotomy scars in newborn (2 to 3 weeks), young (5 to 8 weeks), and older (greater-than-or-equal-to 6 months) dogs at pos tmortem examination 5 months postoperatively. Atriotomy lengths increa sed significantly compared with the initial incision in the newborn (6 .0 mm +/- 0.1 to 15.2 mm +/- 5.8; p < 0.05) and young (6.8 mm +/- 0.9 to 19.6 mm +/- 4.8; p < 0.01) groups but were similar in the older gro up (35.5 mm +/- 11.7 to 27.0 mm +/- 2.5). Ventriculotomy scars grew 11 0 +/- 69% in the newborn group and 126 +/- 71% in the young group but shrank 31 +/- 6% of the original length in the older group (young vs o lder; p < 0.05). This increase in the atriotomy and ventriculotomy sca rs in the young group and the decrease in the older group resulted in scars of similar length; only those scars in the newborn group remaine d significantly shorter than scars in the older group (p < 0.05). Atri otomy and ventriculotomy scars in the older group had more bone or car tilage (p < 0.05) but less dystrophic calcification (p < 0.05) than th ose scars in the younger groups. Atriotomy scars in the two older grou ps had more myocardium (p < 0.05); the young group also had the most m yocardium in ventriculotomy scars. These findings support the hypothes is that there are age-related differences in scar development and comp osition. This may be related to the arrhythmogenic potential of the sc ar.