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Does post-exercise ST depression reflect local ischemia or some global effect in the left ventricle?
Insights
Exercise-induced ST depressions, often seen in lead V5, suggest mechanisms beyond local ischemia. Hemodynamic changes like lower stroke index and higher left ventricular end-diastolic pressure indicate a more ischemic ventricle in affected patients.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Exercise-induced ST depressions (STAE) are common in coronary artery disease, frequently observed in lead V5.
- The precise mechanisms underlying STAE, particularly their prevalence in V5 irrespective of the obstructed artery, remain incompletely understood and may involve factors beyond localized ischemia.
Purpose of the Study:
- To investigate left ventricular (LV) hemodynamics during exercise in patients with severe effort angina.
- To identify hemodynamic parameters that differentiate patients with and without STAE.
- To explore potential global mechanisms contributing to STAE.
Main Methods:
- Studied LV hemodynamics during supine exercise until angina in two groups of patients with severe effort angina: 19 with STAE and 12 without STAE.
- Measured stroke index, left ventricular end-diastolic pressure (LVEDP), and early diastolic pressure (LVeDP).
Main Results:
- Patients with STAE exhibited a significantly lower stroke index (37 vs. 52 ml/m2) and higher LVEDP (40 vs. 30 mmHg) during exercise compared to those without STAE.
- Early diastolic pressure (LVeDP) was the best discriminator (22 vs. 11 mmHg), suggesting a more ischemic ventricle in the STAE group.
- The sum of STAE correlated with LVeDP, not LVEDP, and STAE occurrence positively correlated with R wave height, indicating a potential global mechanism.
Conclusions:
- ST depressions during exercise in patients with coronary heart disease may be influenced by global hemodynamic factors rather than solely local ischemia.
- Elevated early diastolic pressure is a key indicator of ventricular ischemia in patients experiencing STAE.
- The findings suggest a possible link between STAE and compensatory contractility increases in non-ischemic myocardial regions.
Abstract:
As exercise-induced ST depressions are most frequent and marked in lead V5 independent of which single coronary artery is obstructed, some other mechanisms of ST depressions than local ischemia should be searched for. Left ventricular hemodynamics during exercise was studied in two groups of patients with severe effort angina, 19 with and 12 without ST depression after exercise (STAE). During supine exercise until angina, stroke index became significantly lower (37 vs. 52 ml/m2) and left ventricular end-diastolic pressure (LVEDP) significantly higher (40 vs. 30 mmHg) in the STAE group. The best discriminator was the early diastolic pressure (LVeDP) (22 vs. 11 mmHg), which is interpreted as a sign of a more ischemic ventricle in the STAE group. The sum of STAE in all leads is correlated to LVeDP but not to LVEDP during exercise. The link between the significant ischemia in various locations and STAE appearing most frequently and markedly in V5 seems to be some global mechanism as the occurrence of STAE and the height of the R wave were positively correlated in the various leads. As STAE in coronary heart disease shows similar configuration and distribution as in aortic valvular stenosis and digoxin medication of healthy subjects, a possible link could be the compensatory increase in contractility in non-ischemic parts of the ventricle.