In general, coronary angiography with intracoronary injection of acetylcholine or ergonovine is used for identifying VSA. However, it is an invasive procedure which is expensive and requires hospitalisation. One study reported that the sensitivity of hyperventilation combined with cold-pressor stress ECG was 82% in VSA patients.1
Distante et al2
successfully detected coronary spasm using two-dimensional (2D) echocardiography before the onset of chest pain or ST segment elevation on ECG. Furthermore, Hirano et al3
reported that hyperventilation and cold-pressor stress echocardiography was useful for the diagnosis of VSA. However, the evaluation of left ventricular function abnormalities by qualitative estimation of wall thickening is somewhat subjective and requires considerable experience, as demonstrated by differences in sensitivity and specificity between novice and experienced operators. An acute reduction in regional myocardial blood flow causes local contractile dysfunction within a few seconds, which leads to regional deformation.4
Radial thickening and circumferential/longitudinal shortening of ischaemic segments decrease during systole. Segmental relaxation is also impaired during ischaemia; physiological early diastolic thinning and lengthening are replaced by ongoing postsystolic thickening and shortening.4
Changes in early diastolic deformation are proposed as an early marker for regional ischaemia.5
2D strain can evaluate longitudinal and circumferential abnormalities that precede a decrease in radial deformation in ischemia. Since subendocardial myocardial fibres are more susceptible to ischemia, longitudinal function might be altered earlier than radial function.6
This is why longitudinal strains are found to decrease in patients with mild coronary constriction and the administration of low-dose dobutamine.
AFI is a novel algorithm based on speckle-tracking imaging. Automated algorithm provides peak systolic longitudinal strain and postsystolic shortening for each left ventricular segment in a bull's eye plot. AFI provides the objective and accurate evaluation of ischemic wall motion abnormalities based on longitudinal strain. We thus chose AFI for the combination with hyperventilation and cold-pressor stress echocardiography.
In the present case, hyperventilation and cold-pressor stress echocardiography revealed the decreased longitudinal strain which appeared earlier than ECG changes, symptom and wall motion abnormalities, and AFI successfully detected VSA. Further data on the accuracy and usefulness of these non-invasive procedures will establish a new diagnostic method for identifying VSA at outpatient facilities.
- Longitudinal abnormalities precede a decrease in radial deformation in ischemia.
- AFI provides the objective and accurate evaluation of early ischemic wall motion abnormalities based on longitudinal strain.
- The combination of hyperventilation and cold-pressor stress echocardiography and AFI is useful for screening examination for VSA.