Goals and treatment in Heart attack

Once the diagnosis of Myocardial Infarction is considered, care should be taken to decrease the risk of complication. Because dysrhytmia is the most common cause of mortality in the first 24 hour, continuous cardiac monitoring should be instituted immediately.

The goal of therapy is to minimize myocardial tissue loss. In-hospital mortality is closely linked to pump failure. Resuming the balance between oxygen supply and demand is critical to prognosis, morbidity and mortality. Oxygen is to be delivered by mask or nasal cannula. The oxygen content of the blood is a function of saturation and can be determined by blood gas analysis. Nitrates are of benefit by reducing the oxygen demand imbalance and relieving pain. They can be administered orally, sublingually, cutaneously, or intravenously. Blood pressure must be monitored because of vasodilating and venodilating effects of nitrates.

Morphine decreases both cardiac preload and afterload, thereby reducing left-end diastolic pressure. It also significantly reduces pain via analgesia and sedation. The overall affect is a decrease in ventricular work and oxygen consumption.

Excluding a fall in blood pressure, relief of pain is the end point sought by use of nitrates and morphine, not only does this signal a better demand-consumption balance, but it decreases the sympathetic discharge that places added demands upon the myocardium.

Myocardial irritability in the setting of decreased coronary perfusion is caused by a lowering of the ventricular fibrillation threshold, increased automatically, and irregularities in repolarization. Recent evidence [1] has shown that release of endogenous catecholamine plays a significant role. While it was previously thought that multiple premature ventricular complexes were warning arrhythmias, it is now evident [2] that lethal arrhythmias may occur in their complete absence. Primary ventricular fibrillation is by far the most common cause if death in the first 24 hours. Although controversy exists [3], the use of lidocaine, procainamide, or bretylium drip at therapeutic levels is thought to exert a protective influence by raising the threshold for primary ventricular fibrillation.

Updated: March, 02 2008 11:14:55

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