38.2 Cardiovascular Medicine II: Tachyarrhythmias and Bradyarrhythmias, Atrial Fibrillation, Sudden Cardiac Death and Brugada Syndrome, Cardiac Arrest, Valvular and Rheumatic Heart Disease, Infective Endocarditis, Myocarditis and Pericardial Disease

Why this area matters

Rheumatic heart disease remains a common cause of valve disease, atrial fibrillation and stroke in young Filipinos. "Bangungot", the sudden death of young men during sleep, has been linked to Brugada syndrome. Tuberculous pericarditis is still seen. The PLE tests ECG recognition, the first treatment of each arrhythmia, murmurs, and the diagnosis of endocarditis and pericardial disease.

Approach to arrhythmias

• First question: is the patient unstable? Signs are hypotension, shock, altered mental status, ischemic chest pain and acute heart failure.
  • Unstable tachycardia: synchronized cardioversion.
  • Unstable bradycardia: atropine 1 mg IV (repeat every 3 to 5 minutes, up to 3 mg), then transcutaneous pacing or a dopamine or epinephrine infusion.
• Narrow-complex regular tachycardia (SVT):
  • usually AV nodal re-entry;
  • vagal maneuvers (modified Valsalva, carotid massage if no bruit), then adenosine 6 mg rapid IV push, then 12 mg;
  • then a beta-blocker or calcium channel blocker;
  • catheter ablation for recurrence.
• Atrial flutter: sawtooth flutter waves in II, III and aVF, often with 2:1 block at a ventricular rate of about 150. Managed like AF (rate control, anticoagulation, cardioversion), and ablation is highly effective.
• Wolff-Parkinson-White syndrome:
  • short PR, a delta wave and a wide QRS;
  • AF with pre-excitation gives an irregular, very fast wide-complex rhythm;
  • do not give AV nodal blockers (adenosine, beta-blockers, calcium channel blockers, digoxin), which can cause VF;
  • give procainamide or cardiovert, then ablate the pathway.
• Wide-complex tachycardia:
  • treat as VT until proven otherwise, especially with structural heart disease;
  • stable VT: amiodarone 150 mg IV over 10 minutes (or procainamide), or elective cardioversion;
  • torsades de pointes: polymorphic VT with long QT, from drugs (macrolides, fluoroquinolones, antipsychotics, methadone, antiarrhythmics), hypokalemia and hypomagnesemia; give IV magnesium sulfate 2 g and correct electrolytes, with overdrive pacing if needed.
• Sinus tachycardia is a response to fever, pain, hypovolemia, anemia, hypoxia or thyrotoxicosis; treat the cause.

Cardiac Arrhythmias & Resuscitation Protocols

Atrioventricular (AV) Blocks

• First-Degree AV Block: Constant prolongation of the PR interval ($> 0.20\text{ seconds}$ or $> 5$ small squares) with every P wave conducted to a QRS complex. Typically benign; observation without intervention.
• Second-Degree AV Block, Mobitz Type I (Wenckebach): Progressive, gradual lengthening of the PR interval until a P wave fails to conduct (dropped QRS complex). The cycle then resets. Originates at the AV node; usually benign and reversible.
• Second-Degree AV Block, Mobitz Type II: Fixed, constant PR intervals on conducted beats, with intermittent, unexpected non-conducted P waves. Originates below the AV node (His-Purkinje system) and carries high risk of progressing to complete block; indicates permanent pacemaker implantation.
• Third-Degree (Complete) AV Block: Complete atrioventricular dissociation; regular atrial rate (P-P intervals) and independent regular slower ventricular rate (R-R intervals) with no temporal relationship between P waves and QRS complexes. Requires immediate temporary pacing and permanent pacemaker placement.

Atrial Fibrillation (AF)

Atrial fibrillation is characterized by chaotic, disorganized atrial electrical activity without distinct P waves, replaced by irregular fibrillatory waves and an "irregularly irregular" ventricular rhythm.

• Rate versus Rhythm Control: Rate control (target resting heart rate $< 110\text{ bpm}$) uses beta-blockers, non-dihydropyridine calcium channel blockers (diltiazem or verapamil; avoid in HFrEF), or digoxin. Rhythm control (antiarrhythmics like amiodarone, flecainide, propafenone, or direct-current cardioversion) is indicated for persistent symptoms, young patients, or heart failure precipitated by tachycardia.
• Cardioversion Anticoagulation Rule: If AF duration is $> 48\text{ hours}$ (or unknown), therapeutic anticoagulation is mandatory for at least 3 weeks prior to cardioversion and continued for at least 4 weeks post-procedure, unless transesophageal echocardiography (TEE) confirms absence of left atrial appendage thrombus.
• Stroke Risk Stratification ($CHA_2DS_2-VASc$ Score):
  • Congestive heart failure: 1 point
  • Hypertension: 1 point
  • Age $\ge 75$ years: 2 points
  • Diabetes mellitus: 1 point
  • Stroke / TIA / Thromboembolism history: 2 points
  • Vascular disease (prior MI, PAD, aortic plaque): 1 point
  • Age 65-74 years: 1 point
  • Sex category (Female): 1 point
  • Decision Threshold: Score $\ge 2$ in men or $\ge 3$ in women mandates chronic oral anticoagulation. Direct Oral Anticoagulants (DOACs: Apixaban, Rivaroxaban, Dabigatran, Edoxaban) are preferred over Warfarin except in moderate-to-severe mitral stenosis or mechanical prosthetic heart valves.

ACLS Pulseless Arrest: Shockable Rhythms (VT / VF)

For pulseless Ventricular Tachycardia (pVT) and Ventricular Fibrillation (VF):

1. Initiate immediate high-quality cardiopulmonary resuscitation (CPR: rate 100-120/min, depth 2 to 2.4 inches, complete chest recoil, minimize interruptions).
2. Deliver immediate unsynchronized defibrillation (biphasic $120-200\text{ J}$; monophasic $360\text{ J}$).
3. Resume CPR immediately for 2 minutes without pausing for rhythm/pulse checks.
4. Administer Epinephrine $1\text{ mg}$ IV/IO every 3 to 5 minutes starting after the second unsynchronized shock.
5. If VT/VF is refractory after the third shock, administer Amiodarone ($300\text{ mg}$ IV/IO bolus, second dose $150\text{ mg}$) or Lidocaine ($1.0\text{ to }1.5\text{ mg/kg}$ first dose, then $0.5\text{ to }0.75\text{ mg/kg}$).

More on arrest and AF:

• Non-shockable rhythms (asystole, PEA):
  • CPR with epinephrine as soon as possible;
  • search for the reversible causes, the Hs and Ts: hypovolemia, hypoxia, hydrogen ion (acidosis), hypo- or hyperkalemia, hypothermia; tension pneumothorax, tamponade, toxins, and thrombosis (coronary or pulmonary).
• AF in rheumatic mitral stenosis or with a mechanical valve: anticoagulate with warfarin (target INR 2 to 3, or 2.5 to 3.5 for mechanical mitral valves), not DOACs.
• New AF: check thyroid function, echo, electrolytes, and look for alcohol use ("holiday heart"), sleep apnea and valve disease.

Sudden cardiac death

• Causes:
  • coronary artery disease (acute ischemia or scar-related VT): the most common cause in adults;
  • cardiomyopathies: dilated, and hypertrophic cardiomyopathy in young athletes (dynamic outflow murmur that increases with Valsalva and standing);
  • channelopathies: long QT syndrome (triggers include exercise, swimming, loud noises), Brugada syndrome and catecholaminergic VT;
  • WPW and commotio cordis.
• Brugada syndrome:
  • a sodium channel (SCN5A) disorder, most common in young Southeast Asian men;
  • the type 1 ECG shows coved ST elevation of 2 mm or more in V1 to V2 with a right bundle branch block pattern, which can be unmasked by fever or sodium channel blockers;
  • causes VF during sleep, matching the Filipino description of bangungot (sudden unexplained nocturnal death);
  • survivors of arrest and patients with arrhythmic syncope need an ICD; treat fevers promptly and avoid triggering drugs.
• Prevention: an ICD for survivors of VF or sustained VT without a reversible cause, and for primary prevention in selected cardiomyopathies.
• Bystander CPR and early defibrillation (public AEDs) are the main determinants of survival.

Valvular and rheumatic heart disease

Valvular Heart Diseases

• Chronic rheumatic heart disease:
  • follows repeated acute rheumatic fever (group A streptococcal pharyngitis), which is diagnosed by the Jones criteria (see microbiology);
  • mitral stenosis is the classic lesion, often with mitral regurgitation and aortic valve disease;
  • complications of mitral stenosis are atrial fibrillation, stroke, pulmonary hypertension, hemoptysis, hoarseness (Ortner syndrome) and decompensation in pregnancy;
  • secondary prevention is benzathine penicillin G 1.2 million units IM every 3 to 4 weeks, for at least 10 years after the last attack and up to age 40 or longer when valve disease persists;
  • treated with percutaneous balloon mitral commissurotomy for suitable valves, or surgery.
• Other valve lesions:
  • mitral valve prolapse: a mid-systolic click and late systolic murmur;
  • tricuspid regurgitation: a holosystolic murmur at the left lower sternal border that increases with inspiration (Carvallo sign), from pulmonary hypertension or endocarditis in people who inject drugs.
• Dynamic auscultation: most right-sided murmurs increase with inspiration. Murmurs of HCM and MVP increase with Valsalva and standing (less preload), while most others decrease.

Infective endocarditis, myocarditis and pericardial disease

Infective Endocarditis & Pericardial Diseases

Modified Duke Criteria for Infective Endocarditis

Definite diagnosis requires 2 Major Criteria, 1 Major + 3 Minor Criteria, or 5 Minor Criteria:

• Major Criteria:
  1. Positive Blood Cultures: Typical microorganisms consistent with IE from 2 separate blood cultures (Viridans streptococci, Streptococcus gallolyticus, Staphylococcus aureus, or enterococci), or persistently positive blood cultures, or single positive culture for Coxiella burnetii.
  2. Evidence of Endocardial Involvement: Positive echocardiogram demonstrating oscillating intracardiac vegetation, myocardial abscess, new partial dehiscence of a prosthetic valve, or new valvular regurgitation.
• Minor Criteria:
  1. Predisposition (prosthetic valve, prior IE, structural heart disease, IV drug use).
  2. Fever (temperature $\ge 38.0^\circ\text{C}$).
  3. Vascular phenomena (major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, painless erythematous Janeway lesions on palms/soles).
  4. Immunologic phenomena (glomerulonephritis, painful erythematous nodules on pads of digits called Osler nodes, retinal Roth spots, rheumatoid factor).
  5. Microbiological evidence not meeting major criteria.

Acute Pericarditis versus Cardiac Tamponade

• Acute Pericarditis: Presents with sharp, pleuritic retrosternal chest pain that improves sitting up and leaning forward and worsens when supine. Physical exam reveals a high-pitched superficial pericardial friction rub. ECG shows diffuse, concave-upward ST-segment elevation with concurrent PR-segment depression across multiple leads (with reciprocal PR elevation and ST depression in lead aVR). First-line treatment: NSAIDs (ibuprofen $600-800\text{ mg}$ TID) plus Colchicine ($0.5-0.6\text{ mg}$ daily to BID) for 3 months to prevent recurrences.
• Cardiac Tamponade: Accumulation of pericardial fluid under increased pressure impairing ventricular filling. Presents with Beck's Triad (hypotension, jugular venous distension, and muffled/distant heart sounds), tachycardia, and Pulsus Paradoxus (an abnormally large decline in systolic blood pressure of $> 10\text{ mmHg}$ during inspiration). ECG reveals low QRS voltage and electrical alternans (beat-to-beat variation in QRS amplitude). Treatment: Emergent therapeutic pericardiocentesis or surgical pericardial window.

More on endocarditis:

• Organisms:
  • Staphylococcus aureus: acute endocarditis, prosthetic valves, people who inject drugs (tricuspid valve);
  • viridans streptococci: subacute endocarditis on damaged (often rheumatic) valves after dental procedures;
  • enterococci: after genitourinary procedures;
  • Streptococcus gallolyticus (bovis): needs a colonoscopy for colon cancer;
  • culture-negative: prior antibiotics, HACEK organisms, Coxiella, Bartonella.
• Investigations: three sets of blood cultures from separate sites before antibiotics, then echocardiography (transesophageal for prosthetic valves or when the transthoracic study is negative but suspicion is high).
• Treatment:
  • empiric vancomycin plus ceftriaxone (or gentamicin), then targeted therapy for 4 to 6 weeks;
  • surgery for heart failure from valve dysfunction, uncontrolled infection (abscess, heart block), fungal endocarditis, or large vegetations (more than 10 mm) with embolism.
• Prophylaxis:
  • only for highest-risk patients: prosthetic valves or repair material, previous endocarditis, unrepaired cyanotic congenital heart disease and cardiac transplant valvulopathy;
  • only before dental procedures that manipulate the gums or the tooth root area, or perforate the mucosa;
  • amoxicillin 2 g orally 30 to 60 minutes before (azithromycin or doxycycline if allergic; clindamycin is no longer recommended);
  • good oral hygiene matters more.
• Myocarditis:
  • usually viral (coxsackie B, adenovirus, influenza, COVID-19), and rarely after mRNA vaccination in young men; also diphtheria toxin and drugs;
  • chest pain, arrhythmias or heart failure, with raised troponin and normal coronary arteries;
  • cardiac MRI supports the diagnosis;
  • treated supportively (heart failure therapy), with no competitive sport for 3 to 6 months.
• Pericarditis:
  • diagnosed by two of four: pleuritic chest pain relieved by sitting forward, a friction rub, diffuse ST elevation with PR depression, and a new effusion;
  • tuberculous pericarditis is a common cause of large effusions in the Philippines and is treated with anti-TB drugs.
• Constrictive pericarditis:
  • a thick, rigid pericardium, often after TB or radiation;
  • raised JVP, Kussmaul sign (JVP rises on inspiration), a pericardial knock, ascites and edema, and pericardial calcification;
  • treated by pericardiectomy.