Chp 19: Heart Failure & Dysrhythmias (Common Sequelae of Cardiac Diseases)

Conduction System of the Heart

deoxygenated blood: SVC ➡️ SA node ➡️ right atrium ➡️ AV node ➡️ right ventricle ➡️ pulmonary artery

oxygenated blood: left atrium ➡️ mitral valve ➡️ left ventricle ➡️ aortic valve ➡️ aorta ➡️ aorta artery ➡️ systemic circulation

Heart Failure

the inability of the heart to maintain sufficient cardio output to meet metabolic demands of tissues & organs

- RHF: congestion of blood flow in the systemic

- LHF (most common): congestion of blood in the pulmonary venous circulation

- Biventricular HF: both left & right sided heart failure

Clinical Manifestations: Forward Failure

insufficient cardiac pumping manifested by poor CO/hypoxia

- confusion, fatigue, tachycardia, reduced urine output, & poor peripheral circulation

Clinical Manifestations: Backward Failure

congestion of blood behind the pumping chamber/edema

Left-Sided Heart Failure: Forward Effects

Systemic hypoxia & SNS activation

- fatigue, oliguria, anxiety, confusion, increased HR, faint pulses, restlessness

Left-Sided Heart Failure: Backward Effects

Pulmonary congestion & edema

- dyspnea on exertion, orthopnea, & paroxysmal nocturnal dyspnea, cough, respiratory crackles (rales), hypoxemia, & high left-atrial pressure, cyanosis, S3 sound (high pitched)

Paroxysmal Nocturnal Dyspnea

sudden awakening from sleeping with shortness of breath

Right-Sided Heart Failure

- cor pulmonale: right ventricular failure due to pulmonary disease

- increased pulmonary vascular resistance high after load

- right ventricular hypertrophy

Right-Sided Heart Failure: Forward effects

cause low output to left ventricle leading to low CO (systemic hypoxia)

- decrease output to left ventricle ➡️ decrease left ventricular CO ➡️ RAAS activation or decrease tissue perfusion

Right-Sided Heart Failure: Backward Effects

Congestion in the systemic venous system/systemic edema

- decrease ejection fraction ➡️ increase right ventricular preload ➡️ increase right atrial pressure ➡️ systemic congestion

Biventricular Heart Failure

combination of LHF & RHF

- most often result of primary LHF progressing to RHF

Reduced CO in both ventricles

- pulmonary congestion due to LHF

- systemic venous congestion due to RHF

Compensatory mechanisms of heart failure

Baroreceptor receptor: SNS activation

- short term

- increase HR & contractility

RAAS activation: decreased GFR (fluid retention)

- long term

- increase preload

Increase ventricular wall tension: myocyte growth

- hypertrophy

Treatment for HF

- beta-blockers: inhibit SNS effects/reduce afterload

- diuretics: reduce preload

- digitalis: improve CO & contractility

- ACE inhibitors & ARBs: reduce effects of angiotensin II

- pacemakers: synchronize ventricular contraction