Mconnell’s sign is a distinct echocardiographic sign that occurs in Acute pulmonary embolism , where RA and RV dilates. RV shows a distinct regional wall motion abnormality in which RV free wall shows akinesia (or severe hypokinesia ) with well-preserved RV apical contraction.This is visible in apical 4 chamber view.
This sign is explained by both anatomic and hemo-dyanmic reasons.
- RV when exposed to sudden pressure overload it not only dilates , it’s wall stress increases (Laplace law : Wall tension = P x Radius ) and end up mechanically stunned . But , since the RV has a complex shape the distribution of this stress is not uniform .As the RV assumes more spherical shape the apical part is not exposed to this stress as it tend to abut under LV.
- RV apex is anatomically tethered with LV apex and share significant amount of circumferential fibres .In patients with acute pulmonary embolism , LV usually is hyperkinteic due to tachycardia .This pulls the RV apex along with it for a proxy contraction .
- Rarely , primary RV ischemia due to RCA under perfusion* may be responsible for this unique wall motion defect . Since RV apex is mostly supplied by LAD it is free from ischemia . (*Acute elevation of RV intramural pressure due to PHT , compromising RCA perfusion pressure )