Absent septal q wave: a marker of the effects of abnormal activation pattern on left ventricular diastolic function.

OBJECTIVE

To investigate the possible mechanical associations of the presence or absence of the septal q wave.

STUDY DESIGN

Retrospective and prospective study of 63 patients with various left ventricular diseases and 10 controls by electrocardiography, echocardiography, and pulsed Doppler recordings.

SETTING

Tertiary cardiac referral centre.

PATIENTS

73 subjects were studied. 26 had absent septal q waves and a QRS duration < 120 ms, 25 had classic left bundle branch block, and the rest had a normal electrocardiogram. Pathologically, 34 had left ventricular disease and 29 had a structurally normal heart. 10 subjects with structurally normal hearts and normal septal q waves were taken as controls.

RESULTS

The timing of left ventricular minor axis motion was consistently normal in patients with abnormal activation, but long axis motion was considerably altered, with delayed "post-ejection shortening" of a mean amplitude of 4 mm. The post-ejection shortening began 10 (15) ms and reached its peak 90(20) ms after aortic closure (A2). Peak lengthening rate did not differ from normal (6.2 (3.5) v 8.5 (3.5) cm/s, NS) though it occurred significantly later. Post-ejection shortening was unrelated to age, amplitude of left ventricular wall motion, or QRS axis on the surface electrocardiogram. Post-ejection shortening was commoner when QRS duration was > 115 ms, but an absent septal q wave predicted its presence with a specificity of 90% and sensitivity of 86%. In patients with a post-ejection shortening, the onset of left ventricular systolic long axis shortening was delayed and the extent of its lengthening during the pre-ejection period increased, indicating delayed and incoordinate onset of tension development. During diastole, post-ejection shortening was associated with a prolonged isovolumic relaxation period and the time from A2 to the onset of transmitral flow. Peak mitral E wave flow velocity was reduced due to a fall in acceleration time although acceleration rate itself was unchanged.

CONCLUSION

Loss of the normal septal q wave is associated with considerable mechanical consequences throughout the cardiac cycle, from the pre-ejection period to atrial systole, and apparently causes asynchronous subendocardial function.