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Biomedical subjects

C R Wyndham

Publications and source records attributed to C R Wyndham.

79 records · Page 5Linked to original sources
PubMed1976

Prospective observations in patients with chronic bundle branch block and marked H-V prolongation.

Eighteen of 388 patients with chronic bundle branch block, studied electrophysiologically and followed prospectively, had H-V intervals of 80 msec or greater. Five patients were functional class I, five class II, seven class III, and one class IV. Follow-up ranged from 103 to 1919 days (mean 711 +/- 118). Three patients needed permanent pacing for the following indications: sino-atrial block, sinus bradycardia post-cardiac surgery, and 2 degrees block distal to the His bundle. Six patients died, three suddenly, and three nonsudden. The five initially asymptomatic patients are alive and without pacemakers (mean follow-up 732 +/- 139 days). Although marked H-V prolongation was associated with high morbidity and mortality in this small series, this was only in patients with symptomatic heart disease. Asymptomatic patients (five patients) had a benign clinical course. Prophylactic pacing would probably not modify clinical course in the former group, and is probably not indicated in the latter group. Longer follow-up will be needed for definitive prognostication.

Adult↗
PubMed1976

Quantification of human atrioventricular nodal concealed conduction utilizing S1S2S3 stimulation.

We studied antegrade concealed conduction of atrial extrastimuli (A2) that blocked in the atrioventricular (AV) node in eight subjects, using a third extrastimulus (A3), coupled at decreasing coupling intervals to A2. Three A1-A2 intervals were tested in each subject: late (just shorter than AV nodal effective refractory period), intermediate, and early (just longer than atrial functional refractory period). The curves relating the following variables were constructed for each A2: A1-A3, H1-H3 and A2-A3, A3-H3. The former was compared to the control A1-A2, H1-H2 curve. Concealment of A2 was demonstrated in all eight subjects at the three tested values of A1-A2. The A2-A3, A3-H3 curve allowed analysis of AV nodal conduction time (A3-H3) and AV nodal recovery time (defined as the shortest A2-A3 at which the impulse conducted to the His bundle) at identical values of A2-A3. In all subjects the timing of blocked A2 had minimal effect on both AV nodal conduction time and recovery time. In five of the eight subjects a late A2 sporadically conducted to the His bundle. Conduction of A2 to the His bundle resulted in marked lengthening of both AV nodal conduction and recovery times. Concealed conduction of A2 was always demonstrated, but the degree of concealment was relatively fixed, whether A2 was an early, intermediate, or late blocked premature beat. Slow conduction of A2 had a much greater effect than concealment of A2 on subsequent impulse conduction.

Aged↗
PubMed1975

"Supernormal conduction" of a premature impulse utilizing the fast pathway in a patient with dual atrioventricular nodal pathways.

Electrophysiological studies with atrial extrastimulus technique suggested the presence of dual atrioventricular (A-V) nodal pathways in a patient with hypothyroidism, as evidenced by a sudden increase of H1-H2 intervals at critical A1-A2 coupling intervals. Following the atrial extrastimulus (A2), a third impulse (A3) occurred spontaneously. During slow pathway conduction of A2, and A3, appearing at a critically timed interval allowed fast pathway conduction, resulting in an earlier than expected QRS (a form of supernormal conduction). This demonstration of fast pathway conduction during slow pathway conduction adds strong evidence for the existence of dual A-V nodal pathways.

Aged↗
PubMed1975

P-A interval: lack of clinical, electrocardiographic and electrophysiologic correlations.

P-A interval is measured from the onset of the P wave to the onset of the low right atrial electrogram during His bundle recording. The significance of this interval was evaluated in 214 patients with intact A-V conduction and bundle branch block. One hundred fifty-eight patients had normal P-A (NPA) 27 +/- 9, mean +/- SD, and 56 had prolonged P-A (PPA). The NPA and PPA patients were similar (P greater than .10) in regard to sex, age, cardiac functional class, and P-R. PPA patients had significantly (P less than .05) greater P duration (mean +/- SEM, PPA vs NPA) 106 +/- 2 msec vs 100 +/- 1 msec), slower heart rates (72 +/- 2 vs 79 +/- 1), and longer sinus recovery times (1104 +/- 44 msec vs 980 +/- 38 msec). A-H was slightly shorter in PPA than in NPA patients suggesting that a systematic error in measruement of PA due to a relatively distal recording site may have been responsible for PA prolongation in some patients. Patients were prospectively followed for 16-56 months (mean 21.9 +/- 0.8 months). PPA was associated with only minor increase in P wave duration and decrease in sinus automaticity. PPA did not predict future occurrence of significant atrial dysrhythmia.

Arrhythmias, Cardiac↗