MYOCARDIAL INFARCTION-HEART ATTACK

HEART ATTACK(M.I.)

When the heart muscle cells dies with necrosis there is complete blockade of coronary blood supply to heart with prolonged ischemia,and complete occlution of the coronary artery the ultimate result is Myocardial Infarction or Heart Attack.During and after the attack the left ventricle become enlarged and hypertrophied due to the outside pressure.

Etiology:The most common cause is acute thrombus (clot) formation following fissuring and rupture of the lipid rich atherosclerosis plaque and platelet aggregation in the already congested coronary artery. Rare association of the coronary arterial spasm may also contribute to the cause.
Heart Attack is one of the morbid result of prolonged ischemia followed by angina pectoris.
The long time Ischemic Heart Desease caused by decreased blood flow to the heart muscle due to obstruction of the blood flow by the clots,the diffused plaque from the atherosclerosis,followed by platlet aggregation,would certainly leads to MI if left untreated.
Because these condion may kill the heart muscle cells by depriving of oxygen which leads to necrosis and ischemia which will eventually lead to MI.

Sudden death is caused by MI which can trigger the abrupt onset of ventricular fibrillation,the most disorganized and lethal arrhythmia,which can suddenly stop the cardiac output.If this emergency situation is not medically intervened immediately by cordial thump,or defibrillation by counter shock the result is death. 
Generally if there is uncontrolled ventricular fibrillation followed by recusciation occur the situaion is emergency and is known as Sudden Death Syndrom 
In MI a portion of the of the heart muscle suffer prolonged severe supply block of oxygenated blood because of a clot formation,leading to blood vessel damage to form atherosclerosis and platelet aggregations.

Symptoms: 

1.Severe pain radiating from the lower left side to the shoulder.back and neck

2.Shortness of breath

3.Nausea with vomiting or without vomiting;some times stomach pain

4.Hypertention or hypotention

5.Dizziness with headpain,and Fatigue

6.Throat or jawpain

7. Unusual loud snoring with cjocking voice may indicate the presence of sleep apnea,a warning signal to heart attack

8.Sweating

9.Non stopable coughing

10.Diaphoresis (Excretion or oozing of moisture through sweating)

11.Heart murmurs,with tachyarrythmias or bradyarrythmias

25% of the heart attacks are not showing the above symptoms and are silent in eldely patiens,patients with Diabetes and Hypertension

MI can be cassified as 1.Anterior;2.Lateral and 3. Inferior.

But more conveniently and medically classified by ECG as 1.Q-wave MI

2.Non Q-wave MI

What is a Q-wave:-

A Q-wave in an ECG represent any down ward left to right depolarization of the interventricular septum during which ventricles dilates to get filled by blood.See the figure down

In the above ECG look at small downward graphic dip indicated by the arrows and circle.

If there is a problem in the normal depolarizing effects of inter ventricular muscle the Q-wave will be elongated

If this is the condition then there is much chances to get an Q-wave mediated MI.But a problem in Q-wave may not always result to an MI.The presence and elongated  Q-wave indicates there are necrosis.This can be corrected by Coronory bypass surgery if done within a few hours of the post MI.
Generally Q-wave syndroms accounts for 40 to 70% of MI events when compared with non Q-wave MIs.In Q-wave mediated MI there is usually an elevated ST segment.In non Q-wave MIs there is depression in ST-segments.
The most serious warning is a sudden ventricular arrythmia with fibrillation occur without any warnings.

Therapy

 Goals:1.Elimination of clot formations by using Thrombolytics

            2.Releiving Pain

            3.To Prevent arrhythmias

            4.To reduce cardiac workload and stabilize rhythm.

            5.Limiting the affected area and preserving the pump function.

            6.Solving the other complications like nausea,vomiting,stomach aches,arrythmias,blood pressure variations etc.etc.

If not contra indicated four groups of medications can be used in MIs

1.Thrombolytics

2.Beta blockers

3.Nitrates

4.Aspirin

Apart from these Morphine,Lidocaine,Heparine and Warfarine can also be used at times.

The first choice is using thrombolytics such as streptokinase,Urokinase,and Alteplase.as thrombus and embols are the major causes of coronary atherosclerosis plaque apart from LDL and Triglycerides.ACE inhibitors and Calcium channel blockers can also be tried but their efficacy is yet to be proved.

If in case thrombolytics are contraindicated then Percutaneous Transluminal Coronory Angioplasty(PTCA) is proved efficaceous.

Thrombolytic agents were used in patients with suspected MI with prolonged chest pain.

But any benifits that attained by Thrombolytic may seen not immediate but occur as late as 12 hrs.after the pain starts.

Administration of streptokinase IV should be started within 12 hrs and optimally 6 hrs of the pain starts.

Aspirin can be used along with a thrombolytic agent to regulate the circulation in the dosage of 160 mg to 325 mg.for life after the first attack.Get a physicians advice for dosage.

Heparin can be used along with a thrombolytic agent to prevent reocclusion of the coronary artery even heparin is proved in reducing mortality even if it is used without a thrombolytic agent after the first attack.

An IV bolus of 5000 units followed by a continous infusion of 1000 units/hr is its usual dosage.The goal is to maintain the Activated Partial Thromboplastin Time (APTT) between 1 & 1/2 or 2 & 1/2 times normal.

Warfarin can be used in patients with mural thrombus.

Beta Adrenergic blockers propranolo,metoprolol,atenolol,and timolol are commonly used with success.

Nitrates Nitroglycerin is in the most common usage.It should be administered sublingually at the onset of the pain.