Abstract
BackgroundThe majority (60%) of left ventricular (LV) stroke volume (SV) is generated by longitudinal shortening causing apical atrioventricular plane displacement (AVPD) in systole. The remaining SV is caused by radial inward motion of the epicardium both in the septal and the lateral wall. We aimed to determine if these longitudinal, septal and lateral contributions to LVSV are changed in patients with chronic myocardial infarction (MI).MethodsPatients with a chronic (>3 months) ST-elevation MI in the left anterior descending (LAD, n = 20) or right coronary artery (RCA, n = 16) and healthy controls (n = 20) were examined with cardiovascular magnetic resonance (CMR). AVPD was quantified in long axis cine CMR images and LV volumes and dimensions in short axis cine images.ResultsAVPD was decreased both in patients with LAD-MI (11 ± 1 mm, p < 0.001) and RCA-MI (13 ± 1 mm, p < 0.05) compared to controls (15 ± 0 mm). However, the longitudinal contribution to SV was unchanged for both LAD-MI (58 ± 3%, p = 0.08) and RCA-MI (59 ± 3%, p = 0.09) compared to controls (64 ± 2%). The preserved longitudinal contribution despite decreased absolute AVPD was a results of increased epicardial dimensions (p < 0.01 for LAD-MI and p = 0.06 for RCA-MI). In LAD-MI the septal contribution to LVSV was decreased (5 ± 1%) compared to both controls (10 ± 1%, p < 0.01) and patients with RCA-MIs (10 ± 1%, p < 0.01). The lateral contribution was increased in LAD-MI patients (44 ± 3%) compared to both RCA-MI (35 ± 2%, p < 0.05) and controls (29 ± 2%, p < 0.001).ConclusionLongitudinal shortening remains the principal component of left ventricular pumping in patients with chronic MI even when the absolute AVPD is decreased.
Highlights
The majority (60%) of left ventricular (LV) stroke volume (SV) is generated by longitudinal shortening causing apical atrioventricular plane displacement (AVPD) in systole
Left ventricular volumes showed a positive correlation with infarct size, end-diastolic volume (EDV) = 7.3xIS-15.9, r = 0. 75, p < 0.001 and endsystolic volume (ESV) = 7.78xIS-1.6, r = 0.82, p < 0.001
Atrioventricular plane displacement was decreased in both left anterior descending (LAD)-myocardial infarction (MI) (11.0 ± 0.7 mm) and right coronary artery (RCA)-MI (13.0 ± 0.9 mm) compared to controls (15.3 ± 0.4 mm, p < 0.001) but did not differ between the patient groups (p = 0.08)
Summary
The majority (60%) of left ventricular (LV) stroke volume (SV) is generated by longitudinal shortening causing apical atrioventricular plane displacement (AVPD) in systole. We aimed to determine if these longitudinal, septal and lateral contributions to LVSV are changed in patients with chronic myocardial infarction (MI). The relationship is not straightforward but there is an upper limit of ejection fraction determined by infarct size [4]. Myocardial infarction affects longitudinal ventricular function and this can be evaluated as the atrioventricular plane displacement (AVPD) [6]. The interest in longitudinal function has recently increased as global longitudinal strain seem to be a stronger predictor than ejection fraction for mortality [8] and lateral MAPSE from CMR has been shown to be an independent predictive factor for cardiac events [9]
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