Use of power spectral analysis of respiratory sinus arrhythmia to detect graft rejection

: Some evidence has suggested that graft rejection in heart transplant recipients is accompanied by sinus node dysfunction. To test this hypothesis the electrocardiograms of 21 orthotopic heart transplant recipients receiving cyclosporine were recorded at regularly scheduled biopsies. This resulted in 105 good quality recordings of at least 10 minutes each. All exhibited normal sinus rhythm. These recordings were then processed through patented digital routines that calculated the power spectrum of the RR intervals. All recordings exhibited Mayer wave and respiratory sinus arrhythmia (RSA) periodicities. Peak spectral power of RSA (PSP-RSA) demonstrated good repeatability at 2 weeks (r = 0.81). A paired t test comparing the baseline PSP-RSA in eight subjects who experienced rejection episodes with their individual average PSP-RSA during periods of rejection revealed a significant decrease (p = 0.039). As a global measure, PSP-RSA greater than 1 (natural logarithmic scales) demonstrated a sensitivity of 1.0, specificity of 0.42, positive predictive value of 0.22, and negative predictive value of 1.0. These tentative results demonstrate that PSP-RSA may be a sensitive, noninvasive marker for graft rejection of heart transplant patients receiving cyclosporine for immunosuppression. A larger, more extensive study needs to be conducted to confirm these results.