William Heddle

Effects on Cardiac Performance of Atrioventricular Node Catheter Ablation Using Radiofrequency Current for Drug‐Refractory Atrial Arrhythmias

Patients with atrial fibrillation or atrial flutter (AF) are candidates for radiofrequency (RF) catheter ablation of the atrioventricular (AV) node with the aim being to control heart rate. As patients wilh AF can have markedly impaired ventricular function, information concerning the hemodynamic effects of AV node ablation using RF current would be valuable. Fourteen consecutive patients (mean age 65 ± 3 years) with drug‐resistant AF underwent AV node catheter ablation with RF current and had permanent pacemaker implantation. The mean left ventricular ejection fraction (FFJ by two‐dimensional echoeardiography immediately before ablation was 42 ± 3% (range 14%–54%) and their mean exercise time was 4.4 ± 0.4 minutes. Complete AV block was achieved in all 14 patients with 6 ± 2 RF applications (range 1–18). There was no evidence of any acute cardiodepressant effect associated with delivery of RF current, and EF 3 days after ablation was 44 ± 4%. By 6 weeks after ablation, the left ventricular EF was significantly improved compared to baseline (47 ± 4% postablation vs 42 ± 3% preahlation; P < 0.05), and this modest increase in EF was accompanied by an improvement in exercise time (5.4 ± 0.4 min). In conclusion, delivery of RF current for AV node catheter ablation in patients with AF and reduced ventricular function is not associated with any acute cardiodepressant effect. On the contrary, improved control of rapid heart rate following successful AV node ablation is associated with a modest and progressive improvement in cardiac performance.

Examination of an Exponential Model of Conduction Through the Human Atrioventricular Node

The atrioventricular node (AVN) has been modeled by relating output (A2H2 or H1H2) to input (A1A2) where A and H are atrial and His bundle electrograms during fixed rate atrial pacing (A1A1) or with an extrastimulus (A2).

Multiple circus movement tachycardias with multiple accessory pathways

A patient with the Wolff-Parkinson-White syndrome manifesting four types of tachycardia is described. The location and the participation during tachycardia of two different types of accessory atrioventricular pathways were documented during a programmed stimulation study. Unusual modes of initiation of tachycardias were observed, such as the initiation of an orthodromic circus movement tachycardia by an atrial premature beat that conducted in anterograde direction down the accessory pathway.

Value of the 12 lead electrocardiogram in diagnosing type and mechanism of a tachycardia: A survey among 22 cardiologists

Information from programmed electrical stimulation of the heart has improved our ability to diagnose the site of origin and mechanism of a tachycardia from the 12 lead electrocardiogram. To test this hypothesis, the 12 lead electrocardiograms of a 12 year old girl with the Wolff-Parkinson-White syndrome showing four different types of tachycardia were sent for interpretation to 30 leading electrocardiologists , 22 of whom responded. A correct diagnosis of all four tachycardias was made by 13. Three or two of the tachycardias were correctly diagnosed by four and five cardiologists, respectively. The outcome of our study indicates that the pathway and mechanism of tachycardia can frequently be predicted from the 12 lead electrocardiogram alone.

Comparison of exponential and hyperbolic models of conduction through the atrioventricular node.

Conduction through the atrioventricular node (AVN) is assessed during electrophysiology study by relating the output to the input generated by an atrial extrastimulus. This extrastimulus scans electrical diastole of the heart to enable output to be plotted against input. Using this technique, we compared two mathematical models of the AVN, a rectangular hyperbola and a decaying exponential, respectively. The models were compared in 40 curves from 32 patients with only one AVN transmission pathway. Standard errors of the estimate were usually (25/40 trials) less with the exponential model, suggesting this the preferred algorithm for further development.

Sick sinus syndrome and AV node re-entry.

A 69‐year‐old man presented with recurrent palpitations since childhood. Electrophysiology studies performed on two separate occasions revealed the combination of sick sinus syndrome and AV node re‐entrant tachycardia. The case is reported because it illustrates marked temporal variability in the electrophysioiogical properties of the dual AV node pathways, and also deleterious effects of verapamil on sinoatrial node function. (PACE, Vol. 2, May‐June, 1979)

Atrial and His bundle stimulation with an accessory nodo-ventricular connection.

A 39‐year‐old man with a history of frequent paroxysmal tachycardias for 27 years was referred for electrophysiology study. His resting electrocardiogram showed left bundle branch block, which persisted during paroxysmal tachycardia. Electrophysiology study demonstrated the presence of a right‐sided accessory nodo‐ventricular connection.1 The case is of particular importance as it illustrates the diagnostic value of QRS normalization with left atrial pacing and the therapeutic use of rapid His bundle pacing to terminate the tachycardia.

Fast algorithms for the analysis of sino-atrial node function

The calculations of parameters of the sino-atrial node function have previously required the application of a non-linear least squares curve-fitting algorithm. We have compared five algorithms, three of which eliminate the need for direct non-linear least squares routines. The fast algorithms can provide greater accuracy while using less than 10% of the computing time. They make it feasible to provide real-time analysis during clinical electrophysiological studies.