ST Segment Elevation cont..Other Causes

• Coronary vasospasm• Acute Pericarditis• Ventricular Aneurysm• Hyperkalemia• Early Depolarization• Current of Injury- Inability to maintain a normal resting

potential. Resting membrane drops from –90 to –70. Outside of injured cell is more negative, compared to a normal cell, because of leakage of ions resulting in a abnormal baseline.Gives appearance of ST Elevation.

ST Segment Depression

• ST depression is an ECG sign of subendocardial ischemia and injury.

• ST depression is > 1 mm below the baseline, measured .04 second after the J point of the QRS.

• ST depression appears within minutes after the onset of subendocardial non-Q-wave MI, during an anginal attack, or after exercise.

• ST depression quickly reverts to normal after and anginal attack or after exercise as myocardial ischemia is corrected.

ST Segment Depression cont..Other causes:

• Left & Right Ventricular Hypertrophy

• Left & Right Right Bundle Branch Blocks

• Digitalis in Therapeutic and Toxic doses.

Q wave• Normal result from the depolarization of the IS

from left to right.• Abnormal Q waves are signs of irreversible

myocardial necrosis in the evolution of an acute MI.

• Considered abnormal if it is .04 second wide and depth of > 25% of the height of the succeeding R wave.

• Appear in about 2 hours or on the average of 8 to 12 hours after the onset of the MI reaching max in about 24 to 48 hours.

Complications of Acute MI

• Myocardial Dysfunction secondary to myocardial damage resulting in right & left ventricular failure.

• The disruption of the electrical conduction system, resulting in various arrhythmias.

THE ENDOF

CHAPTER 15

Hauszar Robert, Basic Dysrhythmias, Interpretation & Management, Third Edition, Mosby, Inc. 2002, pp. 315-340.