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Absent septal q wave: a marker of the effects of abnormal activation pattern on left ventricular diastolic function
1Cardiac Department, Royal Brompton National Heart and Lung Hospital, London.
Insights
Loss of the septal q wave in electrocardiograms is linked to significant mechanical changes in the left ventricle, affecting heart function from early contraction to atrial systole. This indicates asynchronous subendocardial function.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Biomedical Engineering
Background:
- The septal q wave on an electrocardiogram (ECG) is a normal finding.
- Its absence has been anecdotally associated with left ventricular disease.
- The mechanical implications of absent septal q waves are not well understood.
Purpose of the Study:
- To investigate the mechanical consequences of the presence or absence of the septal q wave.
- To correlate ECG findings with echocardiographic and Doppler measurements of left ventricular function.
Main Methods:
- Retrospective and prospective study of 73 subjects (63 with left ventricular disease, 10 controls).
- Utilized electrocardiography, echocardiography, and pulsed Doppler recordings.
- Subjects categorized by septal q wave presence, QRS duration, and presence of left bundle branch block.
Main Results:
- Absent septal q waves were associated with delayed and altered left ventricular long axis motion, specifically post-ejection shortening.
- Post-ejection shortening was predicted by absent septal q waves with 90% specificity and 86% sensitivity.
- Mechanical alterations extended into diastole, with prolonged isovolumic relaxation and reduced peak mitral E wave flow velocity.
Conclusions:
- The absence of a normal septal q wave signifies substantial mechanical abnormalities throughout the cardiac cycle.
- These findings suggest asynchronous subendocardial function in the absence of septal q waves.
- Septal q wave assessment may provide insights into subtle left ventricular mechanical dysfunction.
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.