3.3 Arrhythmias, Valvular Heart Disease, & Infective Endocarditis

3.3 Arrhythmias, Valvular Heart Disease, & Infective Endocarditis

Quick Summary: In Canada, stroke prevention in Atrial Fibrillation (AF) is stratified using the CHADS65 algorithm, favoring DOACs over Warfarin. Unstable tachycardias require immediate synchronized cardioversion. Severe Aortic Stenosis (triad: Syncope, Angina, Dyspnea) mandates valve replacement once symptomatic. Infective Endocarditis diagnosis relies on the Modified Duke Criteria; antibiotic prophylaxis prior to dental procedures is restricted to high-risk cardiac conditions.

Atrial Fibrillation & Anticoagulation (CHADS65 Algorithm)

Atrial Fibrillation (AF) management focuses on three pillars: stroke prevention, rate control, and rhythm control.

CCS CHADS65 Anticoagulation Decision Tree

The Canadian Cardiovascular Society (CCS) recommends the CHADS65 algorithm for stroke prevention decision-making in non-valvular AF:

• Age ≥65 Years: Prescribe a Direct Oral Anticoagulant (DOAC: Apixaban 5 mg BID, Rivaroxaban 20 mg daily, Dabigatran 150 mg BID, or Edoxaban 60 mg daily).
• Age <65 Years with Risk Factors (Prior Stroke/TIA, HTN, Diabetes, Heart Failure): Prescribe a DOAC.
• Age <65 Years without CHADS Risk Factors but with Vascular Disease (CAD or PAD): Prescribe ASA 81 mg daily.
• Age <65 Years with No Risk Factors & No Vascular Disease: No antithrombotic therapy.

DOACs vs. Warfarin: DOACs are preferred over Warfarin for non-valvular AF due to lower rates of intracranial hemorrhage and all-cause mortality. Exceptions: Warfarin (target INR 2.0–3.0 or 2.5–3.5) remains strictly mandatory for patients with mechanical heart valves or moderate-to-severe mitral stenosis.

Rate vs. Rhythm Control

• Rate Control (First-Line for Most): Target resting HR <110 bpm using Beta-blockers (Metoprolol, Bisoprolol) or Non-dihydropyridine CCBs (Diltiazem, Verapamil).
  • Crucial Rule: Avoid Diltiazem and Verapamil in HFrEF (negative inotropic effect worsens HF); use Beta-blockers or Digoxin.
• Rhythm Control: Reserved for persistent symptoms despite rate control, younger patients, or AF-induced cardiomyopathy. Includes antiarrhythmics (Flecainide, Propafenone in normal structural heart; Amiodarone or Dronedarone in structural heart disease) or Catheter Ablation.

---

Tachyarrhythmias & ACLS Tachycardia Algorithm

Tachycardia Management Principles

1. Unstable Tachycardia: Any tachycardia with hemodynamic instability requires immediate Synchronized Direct-Current Cardioversion (sedate conscious patients first).
2. Stable Narrow-Complex Regular Tachycardia (AVNRT / AVRT / SVT):
   • Step 1: Vagal maneuvers (modified Valsalva maneuver).
   • Step 2: IV Adenosine 6 mg rapid IV push; if unsuccessful, repeat with 12 mg IV push.
   • Step 3: IV Calcium Channel Blocker (Diltiazem) or Beta-blocker.
3. Stable Wide-Complex Tachycardia (QRS ≥0.12s):
   • Treat as Ventricular Tachycardia (VT) until proven otherwise!
   • Administer IV Procainamide (preferred first-line antiarrhythmic) or IV Amiodarone (150 mg IV over 10 minutes).
   • Absolute Warning: Never administer AV nodal blocking agents (diltiazem, verapamil, adenosine) for irregular wide-complex tachycardia or suspected AF with Wolff-Parkinson-White (WPW) syndrome, as this can precipitate fatal Ventricular Fibrillation.
4. Polymorphic VT / Torsades de Pointes: Associated with prolonged QTc. Treat stable patients with IV Magnesium Sulfate (1–2 g IV over 15 min); unstable patients require immediate unsynchronized defibrillation.

---

Valvular Heart Disease

---

Infective Endocarditis (IE)

Infective endocarditis is a lethal infection of the endocardial surface, primarily affecting heart valves.

Etiology & Clinical Stigmata

• Staphylococcus aureus: Most common cause overall, acute rapidly destructive course, affects native valves and IV drug users (tricuspid valve involvement).
• Viridans Group Streptococci: Subacute native valve endocarditis following dental procedures.
• Enterococcus faecalis: Associated with urinary tract or GI procedures.
• Staphylococcus epidermidis: Prosthetic valve endocarditis occurring within 1 year of surgery.

Modified Duke Diagnostic Criteria

Diagnosis requires 2 Major Criteria, 1 Major + 3 Minor Criteria, or 5 Minor Criteria.

• Major Criteria:
  1. Positive Blood Cultures: Typical microorganisms for IE from 2 separate blood cultures, or persistently positive blood cultures.
  2. Endocardial Involvement on Echocardiogram: Oscillating intracardiac mass/vegetation on valve or supporting structures, myocardial abscess, new partial dehiscence of prosthetic valve, or new valvular regurgitation.
• Minor Criteria:
  1. Predisposing heart condition or IV drug use.
  2. Fever ≥38.0°C (100.4°F).
  3. Vascular Phenomena: Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, Janeway lesions (painless erythematous macules on palms/soles).
  4. Immunologic Phenomena: Osler nodes (painful violaceous nodules on fingers/toes), Roth spots (retinal hemorrhages with pale centers), glomerulonephritis, positive Rheumatoid Factor.
  5. Microbiological evidence not meeting major criteria.

Empiric Antibiotic Regimens & Prophylaxis

• Empiric Native Valve IE: IV Vancomycin (15–20 mg/kg q8–12h) + IV Ceftriaxone (2 g daily).
• Empiric Prosthetic Valve IE (<1 year post-op): IV Vancomycin + IV Gentamicin + Oral Rifampin.
• Antibiotic Prophylaxis Indications: Administer Amoxicillin 2 g PO (or Clindamycin 600 mg PO if penicillin allergic) 30 to 60 minutes prior to dental procedures involving manipulation of gingival tissue, ONLY in patients with high-risk conditions:
  1. Prosthetic cardiac valves or prosthetic material used for valve repair.
  2. Previous history of infective endocarditis.
  3. Unrepaired cyanotic congenital heart disease or repaired CHD with residual defects.
  4. Cardiac transplant recipients who develop cardiac valvulopathy. Note: Prophylaxis is no longer recommended for routine GI or GU endoscopic procedures.