What is Subendocardial ischaemia?
What is Subendocardial ischaemia?
Abstract. Most forms of heart disease cause myocardial damage which often is confined to the deep (subendocardial) layer of left ventricular muscle. Much clinical and experimental evidence suggests that subendocardial muscle is prone to ischaemic damage, and a physiological mechanism for this vulnerability is described …
What ECG changes occur with ischemia?
Myocardial ischemic-like ECG changes include ST-segment deviations, T wave inversion, and Q-waves. The earliest manifestations of myocardial ischemia typically involve T waves and the ST segment. It is believed that ECG changes in CCS most often represent preexisting ischemic cardiac disease[32].
What does T wave inversion indicate?
Inverted T waves. Ischemia: Myocardial ischemia is a common cause of inverted T waves. Inverted T waves are less specific than ST segment depression for ischemia, and do not in and of themselves convey a poor prognosis (as compared to patients with an acute coronary syndrome and ST segment depression).
Which of the ECG waveforms is most suggestive of myocardial ischemia?
Although myocardial ischemia may affect every aspect of the ECG – from heart rhythm to QTc interval – the most prominent and reliable ECG changes occur in the ST segment and the T-wave.
How is ischemia found on an ECG?
T wave inversion may be considered to be evidence of myocardial ischaemia if:
- At least 1 mm deep.
- Present in ≥ 2 continuous leads that have dominant R waves (R/S ratio > 1)
- Dynamic — not present on old ECG or changing over time.
How does ischaemia cause ST elevation?
ST segment elevation occurs because when the ventricle is at rest and therefore repolarized, the depolarized ischemic region generates electrical currents that are traveling away from the recording electrode; therefore, the baseline voltage prior to the QRS complex is depressed (red line before R wave).
What causes myocardial ischemia?
Causes of myocardial ischemia Myocardial ischemia occurs when blood flow to the heart muscle (myocardium) is obstructed by a partial or complete blockage of a coronary artery by a buildup of plaques (atherosclerosis). If the plaques rupture, you can have a heart attack (myocardial infarction).
What do flat T waves mean on an ECG?
Flattened T waves are a non-specific finding, but may represent. Ischaemia (if dynamic or in contiguous leads) or. Electrolyte abnormality, e.g. hypokalaemia (if generalised)
What does it mean when the ST segment and T wave change?
ST and T wave changes may represent cardiac pathology or be a normal variant. Interpretation of the findings, therefore, depends on the clinical context and presence of similar findings on prior electrocardiograms.
What are isolated T-wave inversions in myocardial ischemia?
Isolated T-wave inversions in persons presenting with symptoms of myocardial ischemia are referred to as post-ischemic T-wave inversions. To clarify, isolated T-wave inversions indicate that there has been ischemia.
How does subendocardial ischemia cause repolarization?
This wave of repolarization travels away from the overlying recording electrode and therefore displays a positive voltage. Subendocardial ischemia causes subendocardial (Endo in figure) cells to have a shorter action potential duration and therefore an earlier onset of repolarization.
What is the difference between transmural and subendocardial ischemia?
Transmural ischemia implies that the entire wall thickness – from endocardium to epicardium – is affected in the area supplied by the occluded artery. In subendocardial ischemia only the subendocardium is affected.
How do St-T changes in ischemia differ from other conditions?
For example, ST-T changes early in ischemia differs from those in later phases. Moreover, a wide range of other conditions may cause similar ST-T changes and every clinician must be able to differentiate ischemic and non-ischemic ST-T changes. Myocardial ischemia causes changes to the ST segment and T-wave (ST-T changes).
