Establishment of a canine model of cardiac memory using endocardial pacing via internal jugular vein

<p>Abstract</p> <p>Background</p> <p>Development of experimental animal models has played an important role in understanding the mechanisms of cardiac memory. The purpose of this study was to evaluate a new canine model of cardiac memory using endocardial ventricular pacing via internal jugular vein.</p> <p>Methods</p> <p>Twelve Beagle dogs underwent placement of a permanent ventricular pacemaker mimicking the use of pacemakers in humans and induction of cardiac memory by endocardial ventricular pacing.</p> <p>Results</p> <p>Cardiac memory was achieved in 11 of 12 attempts overall. Procedural mortality due to cardiac tamponade (n = 1) occurred in the first attempt. The T-wave memory persisted for 96 ± 17 minutes and 31 ± 6 days in the short-term and long-term cardiac memory groups, respectively. There were no significant differences in the heart rate, blood pressure and echocardiographic parameters in the animals between before and after ventricular pacing in the short-term and long-term cardiac memory groups. No significant pathologic changes with the light microscopy were found in the present study in all dogs.</p> <p>Conclusion</p> <p>The model does require surgery but is not as invasive as an open-chest model. This canine model can serve as a useful tool for studying mechanisms of cardiac memory.</p

Beat-to-beat vectorcardiographic analysis of ventricular depolarization and repolarization in myocardial infarction

OBJECTIVES: Increased beat-to-beat variability in the QT interval has been associated with heart disease and mortality. The purpose of this study was to investigate the beat-to-beat spatial and temporal variations of ventricular depolarization and repolarization in vectorcardiogram (VCG) for characterising myocardial infarction (MI) patients. METHODS: Standard 12-lead ECGs of 84 MI patients (22 f, 63±12 yrs; 62 m, 56±10 yrs) and 69 healthy subjects (17 f, 42±18 yrs; 52 m, 40±13 yrs) were investigated. To extract the beat-to-beat QT intervals, a template-matching algorithm and the singular value decomposition method have been applied to synthesise the ECG data to VCG. Spatial and temporal variations in the QRS complex and T-wave loops were studied by investigating several descriptors (point-to-point distance variability, mean loop length, T-wave morphology dispersion, percentage of loop area, total cosine R-to-T). RESULTS: Point-to-point distance variability of QRS and T-loops (0.13±.04 vs. 0.10±0.04, p<0.0001 and 0.16±.07 vs. 0.13±.06, p<0.05) were significantly larger in the MI group than in the control group. The average T-wave morphology dispersion was significantly higher in the MI group than in the control group (62±8 vs. 38±16, p<.0001). Further, its beat-to-beat variability appeared significantly lower in the MI group than in the control group (12±5 v. 15±6u, p<0.005). Moreover, the average percentage of the T-loop area was found significantly lower in the MI group than the controls (46±17 vs. 55±15, p<.001). Finally, the average and beat-to-beat variability of total cosine R-to-T were not found statistically significant between both groups. CONCLUSIONS: Beat-to-beat assessment of VCG parameters may have diagnostic attributes that might help in identifying MI patients.Muhammad A. Hasan, Derek Abbott and Mathias Baumer

Post-pacemaker T-wave Inversions: Cardiac Memory

This find is registered at Portable Antiquities of the Netherlands with number PAN-0003945