Question

Pathogenesis at the cellular level of Coronary Artery Disease.

Pathogenesis at the cellular level of Left-sided Heart Failure

Describes how Preload, Afterload, and Contractility are affected by Coronary Artery Disease

Describes how Preload, Afterload, and Contractility are affected by Left-sided Heart Failure

Answer 1

Pathogenesis of Coronary Artery Disease

Definition :

Coronary artery disease is a condition where the blood vessels in the heart, the coronary arteries are obstructed or blocked due to the deposition of fatty materials or cholesterol (atherosclerosis) , which results in their damage and can possibly lead to ischemic heart conditions.

Pathogenesis :

Various contributing factors like age,hypertension,obesity etc. can lead to endothelial dysfunction in the coronary arteries and the accumulation of fatty substances will initially form the atherosclerotic plaques.

These formed plaques are then rupture by the action of various inflammatory mediators and cells.When this rupture happens on the exposed plaque forms a clot which may be partial or complete.

This step in turn will result in the build up of collagen and various other tissue factors that will aid in platelet adhesion and its activation releasing thromboxane and ADP from these platelets.The release of these substances will cause these arteries to constrict and further aids in the platelet activation.

When this process continues , the extrinsic coagulation pathway is initiated and forms fibrin clots which obstructs the coronary arteries and results in CAD.

Pathogenesis of Left-Sided Heart Failure

Definition :

Left sided heart failure is a condition where the left ventricle of the heart is affected and the heart fails to pump the blood effectively.

Pathogenesis:

The left sided heart failure is initiated by various contributing factors like uncontrolled high blood pressure , age etc..When this happens there exist very high BP in the arteries and leads to increased workload. In order to make up for the required cardiac output , as a compensatory system the ventricle of the heart enlarges resulting in ventricular hypertrophy.On prolonged effect of this condition , the heart muscles are fatigued and leads to heart failure.

Preload, Afterload, and Contractility are affected by Coronary Artery Disease

Preload is the measure to which the cardiac tissue extends before contraction and afterload is the pressure or force at which the heart should exert to pump out the blood.

In case of Coronary Artery Disease since there is an obstruction, the active flow of blood is hindered and therefore both preload and afterload are reduced.And as a result the contractility also decreases due to obstruction.

Preload, Afterload, and Contractility are affected by Left-sided Heart Failure

As in case of left sided heart failure there is hypertrophy of the left ventricle, there is dilated blood vessel and blood volume.This causes an elevation in the preload and for this reason the afterload is also increased.Due to this the contractility which defines the amount of blood ejected will decrease due to dilation of the vessels.