Heart failure and dysrythmias

What is heart failure?

The inability of the heart to maintain sufficient cardiac output to meet the metabolic demands of tissues and organs. It results from impaired myocardial contraction, relaxation, or both.

What are the most common causes of heart failure?

Myocardial ischemia (CHD) is the most common, followed by hypertension and dilated cardiomyopathy.

What is congestive heart failure? What is the prognosis of HF?

CHF describes HF with symptoms of fluid overload. The slides report a high mortality rate, with approximately 50% of patients dying within five years of diagnosis.

What is systolic heart failure (reduced ejection fractions)?

Impaired ventricular contraction → decreased contractile force → reduced ejection fraction (EF). MI is a common cause; other causes include heart defects, valve disorders, respiratory diseases, and anemia.

What is diastolic heart failure (preserved ejection fraction)?

Impaired ventricular relaxation → stiff, noncompliant LV → inadequate filling. Patients can have low cardiac output, congestion, and edema despite a normal EF.

What is ATP necessary for myocardial relaxation?

ATP is required to remove calcium ions from the cytoplasm during diastole, allowing the myocardium to relax.

What are the 3 major compensatory mechanisms in heart failure?

(1) Increased HR and contractility through SNS activation

(2) increased preload through fluid retention

(3) myocardial hypertrophy

Why do compensatory mechanisms eventually worsen HF?

They initially restore cardiac output but eventually cause harmful structural and functional changes, including increased ventricular workload and afterload.

How does RAAS activation contribute to HF?

Low cardiac output activates RAAS and reduces GFR → fluid retention → increased preload. This temporarily supports output but can worsen congestion.

How does SNS activation compensate for reduced cardiac output?

Baroreceptor responses activate the SNS → increased heart rate and contractility, temporarily improving cardiac output.

What is myocardial hypertrophy in HF?

Increased ventricular wall tension stimulates myocyte growth, initially helping the heart compensate but contributing to harmful cardiac remodeling over time.

What is the difference between forward and backward effects of HF?

Forward effects: inadequate blood pumped forward → decreased cardiac output and tissue perfusion.

Backward effects: blood accumulates behind the failing ventricle → congestion.

What commonly causes left sided HF and what is its cardinal sign?

Often associated with left ventricular infarction. Its cardinal sign is pulmonary congestion.

Explain the backward effects of left sided HF

↓ EF → ↑ LV preload → ↑ left atrial pressure → ↑ pulmonary pressure → pulmonary congestion. Increased pulmonary pressure can also increase RV afterload and cause RV hypertrophy.

What are the backward clinical manifestations of left sided HF?

Dyspnea on exertion, orthopnea, cough, paroxysmal nocturnal dyspnea, cyanosis, and basilar crackles.

What are the forward effects of left sided HF?

↓ cardiac output → decreased tissue perfusion and RAAS activation. Manifestations include fatigue, oliguria, increased HR, faint pulses, restlessness, confusion, and anxiety.

What is right sided HF associated with and what is its primary consequence?

Associated with right ventricular infarction. The primary consequence is systemic venous congestion.

Explain the backward effects of right sided HF

↓ RV EF → ↑ RV preload → ↑ right atrial pressure → systemic venous congestion.

What are the backward clinical manifestations of right sided HF?

Hepatomegaly, ascites, splenomegaly, anorexia, subcutaneous edema, and jugular vein distention (JVD).

What are the forward effects of right sided HF?

↓ blood output to LV → ↓ LV cardiac output → decreased tissue perfusion and RAAS activation. Symptoms include fatigue, oliguria, increased HR, faint pulses, restlessness, confusion, and anxiety.

What is biventricular HF?

Failure of both ventricles, most commonly caused by left-sided HF progressing to right-sided HF. It produces decreased cardiac output, pulmonary congestion, and systemic venous congestion.

What are the primary goals of HF treatment?

Improve cardiac output, minimize congestion, and reduce cardiac workload by manipulating preload, afterload, and contractility.

Which medications improve cardiac output and contractility?

Digitalis/cardiac glycosides improve contractility and output. Beta-agonists can also increase contractility but are not intended for long-term use.

What medications reduce harmful SNS and angiotensin II effects?

Beta-blockers inhibit SNS effects. ACE inhibitors and ARBs reduce the effects of angiotensin II.

How can pacemakers help patients with HF?

They can synchronize ventricular contractions, improving the coordination of cardiac pumping.

What is a dysrhythmia (arrhythmia)?

An abnormality in cardiac rhythm caused by changes in electrical impulse generation or conduction. It may indicate an underlying disorder and impair cardiac output.

What are the 3 major types of dysrhythmias?

Abnormal sinus rhythm rates

impulses generated at abnormal/ectopic sites

disturbances in conduction pathways

What are the characteristics of normal sinus rhythm?

60–100 beats/min, regular rhythm, impulses originating in the SA node, a P wave before every QRS complex, and normal PR, QRS, and QT intervals.W

What is the normal cardiac electrical conduction pathway?

SA node → atria → AV node → His-Purkinje system → ventricular myocardium, producing atrial followed by ventricular contraction.

What factors can cause dysrhythmias?

Hypoxia, electrolyte imbalances (potassium, calcium, sodium), trauma, inflammation, and drugs. Ischemia-related ATP deficiency can contribute to electrolyte disturbances.

Compare sinus tachycardia and sinus bradycardia

Tachycardia: abnormally fast sinus rate (>100 bpm).

Bradycardia: abnormally slow sinus rate (100 bpm**), often associated with myocardial ischemia. It may cause loss of consciousness and can be fatal if not managed quickly.

What is ventricular fibrillation (VF)?

Rapid, uncoordinated ventricular quivering that prevents effective pumping, causing loss of consciousness and potentially death without rapid treatment.

How do ventricular tachycardia and ventricular fibrillation differ?

VT: rapid ventricular rhythm with repeated electrical complexes.

VF: chaotic, uncoordinated ventricular activity without effective coordinated contraction.

Both can be life-threatening.