Cardiac Failure Textbook Notes

Cardiac Failure Definition: Failure of systole, diastole, or both. Consequence: If left untreated, it can lead to cardiac shock. Pathophysiology: An index event might have occurred earlier, which causes the failure. The notes briefly describe cardiac failure, highlighting its nature, potential progression if untreated, and underlying pathophysiology. Cardiac Failure: Detailed Mechanism Causes: Loss of Myocytes Abnormal Myocyte Function Phases of Cardiac Failure: Asymptomatic Phase: Index Events: Initiate compensatory mechanisms to maintain cardiac output. Mechanisms Activated: RAAS (Renin-Angiotensin-Aldosterone System): Increases blood volume and pressure. Increased Sympathetic Drive (e.g., adrenaline): Increases heart rate and contractility. Release of ANP, BNP, PGI2, Bradykinin: Promotes vasodilation and diuresis, reducing blood pressure. Outcome: These mechanisms help maintain normal cardiac output temporarily. Symptomatic Phase: As the disease progresses, structural and functional changes occur. Genetic Changes: Lead to altered protein expression and cellular functions. Neurohormonal Elements: Angiotensin II & Aldosterone: Promote vasoconstriction, fluid retention, and pathological remodeling. Mechanical Overload: Volume and pressure overload contribute to progressive heart damage. Cellular and Molecular Mechanisms: Failure of SERCA Pump: Leads to excessive intracellular calcium (Ca2+), causing calcium overload in the sarcoplasmic reticulum. Results in abnormal phosphorylation of proteins, impairing myocyte function. Activation of Autophagic Pathways: Induces cellular autophagy and apoptosis, contributing to myocyte loss. Fibrotic Tissue Deposition: Leads to reduced ventricular compliance, resulting in diastolic dysfunction and impaired filling. Destruction of Cytoskeletal Proteins: Disruption of key structural proteins like desmin and sarcomeric elements results in myocyte and structural instability. End Result: These processes contribute to left ventricular (LV) remodeling, leading to dilation and impaired contractility. LV Remodeling: Results in progressive diastolic failure and eventual pump failure. Symptoms of Cardiac Failure Dyspnea (Shortness of Breath): Mechanism: Left ventricular (LV) failure leads to accumulation of blood in the left atrium (LA), causing increased backpressure in the pulmonary capillaries and arteries. Result: Pulmonary congestion and fluid accumulation lead to difficulty breathing (dyspnea). Orthopnea: Mechanism: Redistribution of blood from the peripheral veins to the central circulation when lying down increases pressure on the lungs. Result: Worsening of dyspnea when lying flat; the symptom improves immediately after sitting upright. Associated Signs: Edema of the lower limbs and elevated jugular venous pressure (JVP). Paroxysmal Nocturnal Dyspnea (PND): Mechanism: Failure in big airway expansion during sleep due to pulmonary congestion. Timing: Symptoms occur 1-3 hours after falling asleep. Result: Sudden onset of breathlessness during sleep, not relieved immediately by sitting up, unlike orthopnea. Additional Heart Sounds in Cardiac Failure S3 Heart Sound: Cause: Occurs due to systolic dysfunction where there is accumulation of blood in the LV. Result: The turbulence during the passive filling of the ventricle creates the S3 sound. S4 Heart Sound: Cause: Associated with diastolic dysfunction. Reduced ventricular compliance leads to turbulent flow during atrial contraction. Result: The atrial contraction against a stiff ventricle causes the S4 sound. Treatment ACE Inhibitors (ACE I) and Angiotensin II Receptor Blockers (ARBs): These medications are used to delay the remodeling of the left ventricle (LV), helping to manage symptoms and prevent further progression of heart failure.