ST-segment depression

May manifest as tall R waves in the right precordial leads and ST-segment depression in leads Vj - V4... 

Treadmill or bicycle exercise ECG, commonly referred to as a "stress test," is considered positive for IHD if the ECG shows at least a 1 mm deviation of the ST-segment (depression or elevation). 

Risk-stratification of the patient with NSTE ACS is more complex, as in-hospital outcomes for this group of patients varies with reported rates of death of 0% to 12%, reinfarction rates of 0% to 3%, and recurrent severe ischemia rates of 5% to 20%.12 Not all patients presenting with suspected NSTE ACS will even have CAD. Some will eventually be diagnosed with non-ischemic chest discomfort. In general, among NSTE patients, those with ST-segment depression (Fig. 5-1) and/or elevated troponin and/or CK-MB are at higher risk of death or recurrent infarction. 

Fibrinolytic therapy is not indicated in any patient with NSTE ACS, as increased mortality has been reported with fibrinolytics compared to controls in clinical trials in which fibrinolytics have been administered to patients with NSTE ACS (patients with normal or ST-segment depression ECGs).10... 

In patients with NSTE ACS scheduled for early PCI, administration of either abciximab or eptifibatide (double bolus) is recommended. The use of tirofiban in these patients is not recommended, because it has been shown to be inferior to abciximab.2 Medical therapy with glycoprotein Ilb/IIIa receptor inhibitors in patients not undergoing PCI is reserved for higher-risk patients, such as those with positive troponin or ST-segment depression, and patients who have continued or recurrent ischemia despite other antithrombotic therapy.2... 

Acute coronary syndromes Ischemic chest discomfort at rest, most often accompanied by ST-segment elevation, ST-segment depression, or T-wave inversion on the 12-lead electrocardiogram. Furthermore, it is caused by plaque rupture and partial or complete occlusion of the coronary artery by thrombus. Acute coronary syndromes include myocardial infarction and unstable angina. Former terms used to describe types of acute coronary syndromes include Q-wave myocardial infarction, non-Q-wave myocardial infarction, and unstable angina. 

Exercise tolerance (stress) testing (ETT) is recommended for patients with an intermediate probability of CAD. Results correlate well with the likelihood of progressing to angina, occurrence of acute MI, and cardiovascular death. Ischemic ST-segment depression during ETT is an independent risk factor for cardiovascular events and mortality. Thallium myocardial perfusion scintigraphy may be used in conjunction with ETT to detect reversible and irreversible defects in blood flow to the myocardium. 

For variant angina, reduction in symptoms and nitroglycerin consumption as documented by a patient diary can assist the interpretation of objective data obtained from ambulatory ECG recordings. Evidence of efficacy includes the reduction of ischemic events, both ST-segment depression and elevation. Additional evidence is a reduced number of attacks of angina requiring hospitalization, and the absence of MI and sudden death. 

ECG changes include increased heart rate, flattened T waves, ST-segment depression, prolongation of QT and PR intervals, and torsade de pointes. Torsade de pointes has been reported with thioridazine, which may be a cause of cardiac sudden death. 

Cardiovascular manifestations include hypertension and cardiac arrhythmias (e.g., heart block, atrial flutter, paroxysmal atrial tachycardia, ventricular fibrillation, and digitalis-induced arrhythmias). In severe hypokalemia (serum concentration <2.5 mEq/L), ECG effects include ST-segment depression or flattening, T-wave inversion, and U-wave elevation. 

Severe hyperkalemia may produce arrhythmias, bradycardia, and ECG changes (tented T waves, widening QRS complex, and ST segment depression). These may proceed to cardiac standstill or ventricular fibrillation. 

Triamterene use may result in hyponatremia (somnolence, dry mouth, increased thirst, lack of energy) or severe hyperkalemia (irritability, anxiety, heaviness of legs, paresthesia, hypotension, bradycardia, ECG changes (tented T waves, widening QRS complex, ST segment depression]), particularly in those with renal impairment or diabetes, the elderly, or severely ill patients. 

A previously fit 19-year-old woman had severe ST segment depression and increased troponin concentrations after a bolus dose of oxytocin 5 units (8). 

Before arrhythmias Negligible tPR interval o.QT interval T wave inversion ST segment depression... 

Patients The selection of patients for thrombolytic therapy is critical. The diagnosis of acute myocardial infarction is made clinically and is confirmed by electrocardiography. Patients with ST segment elevation and bundle branch block on electrocardiography do best those with ST segment depression or a normal ECG do less well and those with non-Q-wave acute myocardial infarction may even be harmed. All trials to date show the greatest benefit for thrombolytic therapy when it is given early, within 6 hours after symptomatic onset of acute myocardial infarction. 

In rabbits burned by an unknown amount of white phosphorus, electrocardiogram alterations (prolongation of QT interval, ST segment depression, T-wave changes, bradycardia, and low voltage QRS complex) indicative of myocardial damage were observed however, no histological alterations were observed in the heart (Bowen et al. 1971). 

Hypokalemia results in decreased T-wave amplitude and ST-segment depression however, accurate QT interval measiuement is difficult. Malignant ventricular arrhythmias result when potassium concentrations become very low. Hypercalcemia shortens the QT interval while hypocalcemia produces ST-segment prolongation. 

In 7800 patients with chest pain and either ST segment depression or a positive troponin test, the addition of abciximab to unfractionated heparin or low molecular weight heparin in the treatment of acute coronary syndrome was not associated with any significant... 

Ritodrine can cause bradycardia instead of the expected tachycardia (SEDA-8, 145) an unexpected hypertensive crisis has also been reported (SEDA-8,145). ST segment depression is a consistent finding in patients during ritodrine infusion, and should therefore not always be... 

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