Exploring cardiac vector propagation in acute myocardial infarction: a spatial velocity perspective.

Aims: To objectively characterize the spatial-velocity dynamics of the QRS-loop in the vectorcardiogram (VCG) of patients with acute myocardial infarction (AMI).

Methods: VCG was constructed as a space curve directly with three quasi-orthogonal leads I, aVF and V2 recorded by conventional ECG of 25 healthy individuals and 50 AMI patients. Spatial velocity (SV) of the dynamic QRS loop, spatial distance (SD), and spatial magnitude (SM) were recorded, along with axis-specific component attributes of vector magnitude such as ΔX, ΔY, and ΔZ.

Results: Decreased SV (12-25%, p = 0.02) and SD (10-26%, p = 0.02) and altered spatial propagation patterns of ventricular vectors in AMI were recorded, with changes in specific axes based on infarct location. Significant vector changes were found in the Y-Axis in IWMI (p = 0.005) and X-Axis in cases of AWMI (p = 0.02), as compared to controls. There was no apparent alteration of SM in AMI.

Conclusion: Decreased SV and SD without any significant alteration of SM indicates close approximation and clustering of the tips of the ventricular vector in AMI. This may be due to dilation, thinning, and stress of the ventricular wall in early post infarction ventricular remodeling, along with relative ischemia due to associated tachycardia and higher myocardial oxygen demand.