Heart Failure Chapter 19

Study Notes

Heart failure occurs when cardiac output is insufficient to meet the body's oxygen needs.
It is a progressive condition, characterized by gradual cardiac performance decline and episodes of acute decompensation, often requiring hospitalization.
Major causes include coronary artery disease and hypertension.

Systolic Failure
- Involves reduced mechanical pumping action and decreased ejection fraction.
Diastolic Failure
- Characterized by stiffening and inadequate relaxation, leading to reduced filling and cardiac output.
- Ejection fraction may be normal, although stroke volume is significantly decreased.

Common symptoms include tachycardia, decreased exercise tolerance, shortness of breath, peripheral and pulmonary edema, and cardiomegaly.

Rare form where the body's demands exceed even increased cardiac output.
Associated conditions include hyperthyroidism, beriberi, anemia, and arteriovenous shunts.

Increased sympathetic activity and activation of the Renin-Angiotensin-Aldosterone System (RAAS) occur.
Myocardial hypertrophy is a critical intrinsic mechanism to maintain cardiac performance despite potential adverse effects.

Signifies increased muscle mass, aiding cardiac performance but may lead to ischemic changes and impaired diastolic filling.

Refers to dilation and structural changes in the stressed myocardium, occurring over time due to heart failure.

Preload
- Generally increased due to higher blood volume and venous tone, defined as initial stretching of cardiac myocytes prior to contraction.
Afterload
- Resistance the heart faces when pumping blood, represented by aortic impedance and systemic vascular resistance.
Contractility
- Patients exhibit reduced intrinsic contractility, but can still respond positively to inotropic drugs.
Heart Rate
- An essential determinant of cardiac output and the first compensatory mechanism, typically increased via sympathetic activation.

Digitalis
- A cardiac glycoside obtained from plants such as Digitalis lanata, used to treat heart failure.
Digoxin (Lanoxin®)
- Inhibits Na+/K+ ATPase, increasing calcium availability in the heart muscle, thereby enhancing contractility (inotropic effect).

Increases cardiac contractility and has a parasympathomimetic effect, slowing heart rate and conduction.

Symptoms include nausea, vomiting, diarrhea, cardiac arrhythmias, disorientation, visual disturbances, and gynecomastia.
Interactions with potassium, calcium, and magnesium can influence digoxin's effects, emphasizing the importance of electrolyte balance.

Istaroxime
- Investigational drug that enhances contractility by Na+/K+ ATPase inhibition and facilitates calcium sequestration in the sarcoplasmic reticulum.
Levosimendan
- Sensitizes the troponin system to calcium, with potential positive inotropic effects.