Tuesday, November 13, 2012

CARDIAC DISEASES


Congestive Heart Failure (CHF):

This is a condition in which heart cannot pump adequate blood to meet body need, causing pulmonary edema as a result of blood retention. Also generalized edema is seen. This occurs due to loss of cardiac tissue and function. This occurs for example by loss of tissue during AMI, cardiac stiffness which restrict filling and increase in peripheral demand like during emotion, stress, other causes like inflammatory heart disease, cardiomyopathies.

Acute Coronary Syndrome (ACS):

It encompasses patients who present with unstable ischemic heart disease. It includes both unstable angina and AMI. Ischemia usually occurs when circulation to region of heart is blocked that affects coronary artery and there is acute response of coronary artery to ischaemia. If ischemia is high grade or prolonged then necrosis or infarction ensues and cause AMI.

Ischemia causes the depletion of ATP and ADP as anaerobic metabolism produce less ATP. The resulting intracellular acidosis due to lactate formation inactivates membrane ion pumps causing an influx of calcium ions, which activates intracellular phospholipase causing membrane structure disruption. The reduced blood flow also hinders efficient removal of metabolites from circulation which will increase the intracellular oncotic pressure resulting in cell swelling, affect permeability of cell membrane.

There are two types of MI, if patients have STE, they are called STEAMI and if they do not have STE but have biochemical criteria for cardiac injury they are called NSTEMI and accounts for 70% of cases. STEAMI usually develops Q waves but in NSTEMI there is no Q wave.
 







A is normal pattern; B is the STEAMI and occurs hours after infarction. Ischemia without necrosis is called Angina. C is STEAMI with larger Q waves and develops hours to days later.

The major cause of ACS is atherosclerosis that causes plaque disruption and subsequent thrombus formation occluding the coronary artery. In all AMI left ventricle is mostly affected with occasional involvement of left ventricles.

STEAMI occurs in the morning hours soon after arising, a period of increasing adrenergic activity, increased fibrinogen, increased inhibition of fibrinolysis, increased platelet adhesiveness, this occurring at about 8 AM to 9 AM and also at 5 PM. STEAMI is associated with higher early mortality occurring within 6 months or 30 or 40 days. But NSTEMI has longer survival rate.

The classification scheme for unstable angina was established by Braunwald. A totally occluded clot produces AMI. Both AMI and UA, can produce chest pain at rest, lead to changes in electrocardiogram and release of enzymes and proteins into blood. In Angina there is partial blockage leading to severe compressive referred chest pain at rest or excursion and in AMI there is large blockage causing necrosis, infarction, also has similar symptoms plus biochemical findings. 
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