2.3 Valvular Disorders, Vascular Diseases & Aortic Pathologies

2.3 Valvular Disorders, Vascular Diseases & Aortic Pathologies

[!NOTE] ANCC Clinical Scope: Domain I demands advanced proficiency in identifying valvular murmurs, hemodynamic loading conditions, peripheral vascular signs, and cardiovascular emergencies including infective endocarditis, cardiac tamponade, and acute aortic dissection.

Structural valve defects, peripheral vascular insufficiency, and acute aortic syndromes require rapid physical assessment, hemodynamic differentiation, and targeted emergency management.

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Valvular Heart Disease: Stenosis vs. Regurgitation

Valvular lesions impose either a pressure overload (stenotic obstruction) or a volume overload (regurgitant incompetence) on the myocardium:

• Pressure Overload (Stenosis): Forces the chamber to contract against elevated resistance, inducing concentric hypertrophy (sarcomeres added in parallel). Wall thickness ($h$) increases relative to cavity radius ($r$), normalizing systolic wall stress (Laplace's Law: $\sigma = P \times r / 2h$) but decreasing diastolic compliance.
• Volume Overload (Regurgitation): Subjected to retrograde diastolic or systolic flow, the chamber develops eccentric hypertrophy (sarcomeres added in series), resulting in progressive chamber dilation.

1. Aortic Stenosis (AS)

• Etiology: Age-related calcific degeneration, congenital bicuspid aortic valve (symptomatic at age 40–60), or rheumatic fever.
• Pathophysiology: Orifice narrows from normal ($3.0-4.0\text{ cm}^2$) to severe ($\le 1.0\text{ cm}^2$ or mean gradient $>40$ mmHg). LV develops marked concentric hypertrophy. Stiff, non-compliant LV becomes highly dependent on atrial kick.
• Clinical Triad: Angina, Syncope, Dyspnea (SAD).
• Auscultation & Signs: Harsh crescendo-decrescendo systolic ejection murmur at the right 2nd intercostal space (RSB) radiating to the carotids; single or paradoxical splitting of $S_2$; and pulsus parvus et tardus (weak, delayed carotid upstroke).

2. Aortic Regurgitation (AR)

• Etiology: Aortic root dilation (hypertension, Marfan syndrome, dissection), infective endocarditis, bicuspid valve, or rheumatic disease.
• Pathophysiology: Incomplete diastolic leaflet closure permits blood to leak retrograde into the LV, producing combined volume and pressure overload. The LV undergoes massive dilation and eccentric hypertrophy. Diastolic runoff causes aortic diastolic pressure to plunge, producing a widened pulse pressure (e.g., 160/40 mmHg).
• Auscultation & Signs: High-pitched, blowing decrescendo diastolic murmur at left 3rd–4th ICS (Erb's point) with the patient leaning forward in end-expiration. An Austin Flint murmur (apical mid-diastolic rumble) may occur from regurgitant jet impingement on the mitral leaflet. Peripheral signs include water-hammer (Corrigan's) pulse and Quincke's capillary pulsations.

3. Mitral Stenosis (MS)

• Etiology: Predominantly rheumatic heart disease; annular calcification in elderly.
• Pathophysiology: Commisural fusion narrows the valve (severe: $\le 1.5\text{ cm}^2$), obstructing diastolic filling from the LA to the LV. Elevated left atrial pressure causes marked left atrial enlargement, pulmonary venous congestion, secondary pulmonary hypertension, and right-sided heart failure. Chronic LA stretch frequently triggers atrial fibrillation, creating high risk for left atrial appendage thrombus and embolic stroke.
• Auscultation & Signs: Snappy $S_1$ followed in early diastole by a sharp Opening Snap (OS), leading into a low-pitched rumbling mid-diastolic murmur with presystolic accentuation at the apex in the left lateral decubitus position.

4. Mitral Regurgitation (MR)

• Etiology: Primary: Mitral valve prolapse (MVP), infective endocarditis, chordae rupture, or papillary muscle rupture. Secondary (Functional): Ischemic LV dilation displacing papillary muscles.
• Pathophysiology: Systolic leakage from the LV into the LA. In chronic MR, gradual LA and LV dilation accommodates volume over years. In acute MR (e.g., papillary rupture), a normal, non-compliant LA receives a sudden volume surge, causing giant v-waves ($>40-50$ mmHg) on the PAOP waveform, acute flash pulmonary edema, and cardiogenic shock.
• Auscultation & Signs: Blowing holosystolic murmur at the apex radiating to the left axilla; diminished $S_1$; $S_3$ gallop. In MVP, a mid-systolic click precedes a late systolic murmur.

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Infective Endocarditis (IE): Pathogenesis & Duke Criteria

Infective endocarditis is an infection of the endocardial surface:

1. Pathogenesis: Turbulent flow causes endothelial damage, forming a sterile non-bacterial thrombotic endocarditis (NBTE) platelet-fibrin nidus. Transient bacteremia (Staphylococcus aureus, Streptococcus viridans, Enterococcus) colonizes the nidus, growing into an infected vegetation encased in fibrin that impairs antibiotic penetration.
2. Modified Duke Criteria (Definite IE = 2 Major, 1 Major + 3 Minor, or 5 Minor):
   • Major Criteria: 1) Positive blood cultures for typical organisms from $\ge 2$ separate cultures; 2) Echocardiographic evidence of vegetation, perivalvular abscess, new prosthetic dehiscence, or new regurgitation.
   • Minor Criteria: Predisposition (prosthetic valve, prior IE, IVDU); Fever $\ge 38.0^\circ\text{C}$; Vascular phenomena (arterial emboli, septic pulmonary infarcts, Janeway lesions [painless red macules on palms/soles]); Immunologic phenomena (glomerulonephritis, Osler nodes [painful violaceous nodules on finger/toe pads], Roth spots [retinal hemorrhages with pale centers]); Microbiological evidence not meeting major criteria.
3. Critical Complications: Vegetative embolization (stroke, splenic/renal infarcts, septic PE in tricuspid IE); acute valve leaflet destruction; and perivalvular ring abscess, classically signaled by a newly prolonged PR interval (first-degree AV block) on ECG.

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Pericarditis vs. Cardiac Tamponade

In cardiac tamponade, elevated intrapericardial pressure compresses all four chambers. Because the pericardial sac is rigid, ventricular interdependence occurs: during inspiration, increased RV filling pushes the interventricular septum into the LV cavity, decreasing LV stroke volume and dropping systolic blood pressure by $>10$ mmHg (pulsus paradoxus).

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Peripheral Vascular Diseases: PAD, CVI & DVT

• Peripheral Arterial Disease (PAD): Atherosclerosis of lower extremity arteries. Presents with intermittent claudication (reproducible exertional calf pain relieved by rest) and progresses to ischemic rest pain (burning foot pain at night, relieved by dependency). Signs include dependent rubor, pallor upon leg elevation, cool skin, hair loss, diminished pulses, and deep, punched-out ulcers on toes/heels.
  • Ankle-Brachial Index (ABI): Ratio of ankle to brachial systolic blood pressure.
    • 1.00 – 1.40: Normal.
    • 0.91 – 0.99: Borderline.
    • 0.41 – 0.90: Mild-to-Moderate PAD (lifestyle modification, antiplatelets, statins, cilostazol).
    • $\le 0.40$: Severe PAD / Critical Limb Ischemia (urgent revascularization).
    • $>1.40$: Non-compressible, calcified arteries (diabetes, ESRD); evaluate with Toe-Brachial Index (TBI).
• Chronic Venous Insufficiency (CVI): Venous valve incompetence and ambulatory venous hypertension. Erythrocyte breakdown deposits hemosiderin (rusty brown pigmentation) in perimalleolar skin, with brawny edema, subcutaneous fibrosis (lipodermatosclerosis), and shallow, irregular, wet ulcers over the medial malleolus.
• Deep Vein Thrombosis (DVT): Governed by Virchow's Triad (endothelial injury, venous stasis, hypercoagulability). Presents with unilateral calf pain, erythema, warmth, and edema; diagnosed by compression venous ultrasound. Complication: pulmonary embolism.

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Aortic Aneurysms & Acute Aortic Dissection

• Aortic Aneurysms: Permanent dilation $\ge 50%$ of normal diameter involving all three wall layers. Abdominal Aortic Aneurysms (AAA) occur infrarenally. Risk factors: smoking, male sex, hypertension, age $>65$. Ultrasound screening is recommended for men aged 65–75 who have smoked. Elective repair indicated at $\ge 5.5\text{ cm}$ in men ($\ge 5.0\text{ cm}$ in women). Rupture presents with the triad of abdominal/back pain, pulsatile mass, and severe hypotension.
• Acute Aortic Dissection: An intimal tear allows pressurized blood into the media, separating vessel layers into a true and false lumen.
  • Stanford Type A: Involves the ascending aorta. Surgical emergency due to risks of tamponade (rupture into pericardium), acute aortic regurgitation, ostial coronary occlusion (inferior STEMI), and stroke.
  • Stanford Type B: Confined to the descending aorta distal to the left subclavian artery. Managed medically in the ICU unless complicated (malperfusion, rupture) requiring TEVAR.
  • Clinical Presentation: Sudden, severe chest or back pain described as "ripping or tearing"; systolic BP differential $>20$ mmHg between arms; pulse deficits; new diastolic AR murmur.

[!IMPORTANT] Medical Anti-Impulse Therapy: The priority in acute dissection is to reduce aortic shear stress ($dP/dt$) and blood pressure:

1. Target Heart Rate $<60\text{ bpm}$ and Systolic Blood Pressure $100\text{ to }120\text{ mmHg}$.
2. Administer IV Beta-Blockers (esmolol or labetalol) FIRST. Vasodilators (nicardipine, nitroprusside) given before beta-blockade induce reflex tachycardia, which increases $dP/dt$ and can propagate the dissection.