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Significance of retrograde conduction in A-v dissociation.

1965; BMJ; Volume: 27; Issue: 6 Linguagem: Inglês

10.1136/hrt.27.6.896

1468-201X

L Schamroth, Hermann Friedberg,

Particle accelerators and beam dynamics

In certain circumstances the discharge rate of the A-V node may exceed that of the S-A node.The A-V node then becomes the dominant pacemaker of the heart.If, in addition, there is retro- grade unidirectional A-V block, the atria remain under control of the S-A node, and A-V dissocia- tion results.When a sinus impulse reaches the A-V node during the non-refractory phase, it is conducted to, and captures control of, the ventricles for one beat-known as a capture beat; occasionally 2, or rarely 3, consecutive capture beats occur.An analogous situation may arise when the ectopic pacemaker is situated in the ventricles.This communication reports further observations on A-V nodal conduction in A-V dissociation, with special reference to conduction in consecutive capture beats.A-V DISsOCIATIoN WITH PAIRED CONSECUTIVE CAPTURE BEATS Case 1.The electrocardiogram (Fig. 1) shows dissociation between sinus and A-V nodal rhythms.The sinus cycle is regular at 112*; the A-V nodal cycle is regular at 110.The first 4 QRS complexes are A-V nodal beats.The next 2 QRS complexes (labelled R3 and R4) are premature and represent con- secutive ventricular captures.The next QRS complex is slightly premature (106) and probably represents a third consecutive ventricular capture.The P-R interval of the first capture beat is 76; that of the second 25.The R-R interval terminated by the first capture beat-the capture interval-is 86; the second capture interval is 62.Case 2. The electrocardiogram (Fig. 2) shows dissociation between rapid sinus and A-V nodal rhythms.The sinus cycle is regular at 52; the A-V nodal cycle is regular at 47.The first 4 QRS complexes represent A-V nodal beats; the next 2 QRS complexes (labelled R3 and R4) are premature and represent consecutive ventricular captures.The P-R interval of the first capture beat is 34; that of the second 22.The first capture interval is 42; the second 37.Case 3. The electrocardiogram (Fig. 3) shows dissociation between sinus and A-V nodal rhythms- sinus and A-V nodal tachycardia.The sinus cycle is regular at 56; the A-V nodal cycle is regular at 48.The first 3 QRS complexes are A-V nodal beats; the next 2 QRS complexes (labelled R3 and R4) are pre- mature and represent consecutive ventricular captures.The P-R interval of the first capture beat is 30; that of the second 16.The first capture interval is 34; the second 42.The first capture beat is conducted with slight aberration.Case 4. The electrocardiogram (Fig. 4) shows dissociation between sinus and A-V nodal rhythmssinus and A-V nodal tachycardia.The sinus cycle is regular at 52; the A-V nodal cycle is regular at 50.The first 4 QRS complexes are A-V nodal beats; the next 2 QRS complexes (labelled R3 and R4) are pre- mature and represent consecutive ventricular captures.The P-R interval of the first capture beat is 23; that of the second 16.The first capture interval is 37; the second 43.The first capture beat is conducted with aberration.* All time intervals represent hundredths of a second, e.g.62=62 hundredths of a second.