Cardiovascular Collapse, Cardiac Arrest, and Sudden Cardiac Death¶
Chapter 317 | Part 8: Critical Care Medicine · Part 8 – Critical Care Medicine · Chapter 317
Key Clinical Points¶
- Sudden cardiac death (SCD) accounts for 15% of all deaths and 50% of all cardiac deaths in the United States.
- Ventricular fibrillation (VF) is the most common initial rhythm in public locations, but pulseless electrical activity (PEA) and asystole are more common in unwitnessed arrests.
- Survival rates for out-of-hospital cardiac arrest are highest for shockable rhythms (VF/VT) with immediate defibrillation and CPR.
- Therapeutic hypothermia (targeted temperature management) at 32–37.5°C for ≥ 24 hours is recommended for comatose patients post-ROSC.
- Implantable cardioverter defibrillators (ICDs) are indicated for VT/VF without clearly reversible causes, but not for end-stage heart disease with minimal survival prospect.
- Reversible causes of cardiac arrest (H's and T's) must be identified and treated: Hypoxia, Hypovolemia, Hydrogen ions (acidosis), Hyperkalemia/Hypokalemia, Hypothermia, Tension pneumothorax, Tamponade, Toxins, Thrombosis (PE/MI).
- Approximately 70% of SCDs in white men are due to coronary artery disease (CAD), compared to 40–50% in women and blacks.
- SCD rates are lower in Asia (52.5 per 100,000) compared to Europe (86.4 per 100,000), North America (98.1 per 100,000), and Australia (111.9 per 100,000).
- In unwitnessed cases, the definition of SCD is often expanded to include unexpected deaths where the subject was documented to be well within the preceding 24 hours.
- Noncardiac causes such as pulmonary embolism, stroke, and aortic dissection cannot be excluded without an autopsy in unwitnessed sudden deaths.
DEFINITION & OVERVIEW¶
• Cardiovascular Collapse: Defined as severe hypotension from acute cardiac dysfunction or loss of peripheral vasculature resistance resulting in cerebral hypoperfusion and loss of consciousness. • Sudden Cardiac Arrest (SCA): An abrupt loss of cardiac function resulting in complete cardiovascular collapse due to an acute life-threatening cardiac arrhythmia or abrupt loss of myocardial pump function requiring emergency medical intervention for restoration of effective circulation. • Sudden Cardiac Death (SCD): Sudden unexpected death attributed to cardiac arrest, which occurs within 1 hour of symptom onset. In unwitnessed cases, the definition is often expanded to include unexpected deaths where the subject was documented to be well within the preceding 24 hours.
Distinction Between Terms¶
• Cardiovascular Collapse: Broad term; includes cardiac arrest as well as transient events that characteristically revert spontaneously (e.g., neurocardiogenic syncope, transient hypotension). • Cardiac Arrest: Abrupt cessation of cardiac function resulting in loss of effective circulation; rarely reverses spontaneously; likelihood of success depends on mechanism, setting, and speed of intervention. • Sudden Cardiac Death: Sudden unexpected death attributed to cardiac arrest (within 1 hour of symptom onset).
Table 317-1: Distinction Between Cardiovascular Collapse, Cardiac Arrest, and Death | TERM | DEFINITION | QUALIFIERS | MECHANISMS | | --- | --- | --- | --- | | Cardiovascular collapse | Sudden loss of effective circulation due to cardiac and/or peripheral vascular factors that may reverse spontaneously (e.g., neurocardiogenic syncope, transient hypotension) or require interventions (e.g., hypovolemia, tamponade, ventricular fibrillation). | Broad term that includes cardiac arrest as well as transient events that characteristically revert spontaneously presenting as syncope. | Same as cardiac arrest, plus neurocardiogenic syncope or other causes of transient loss of blood flow. | | Cardiac arrest | Abrupt cessation of cardiac function resulting in loss of effective circulation that may be reversible by prompt emergency medical intervention. | Rare spontaneous reversions; likelihood of successful intervention relates to mechanism of arrest, clinical setting, availability of emergency medical services, and prompt return of circulation. | Ventricular fibrillation, ventricular tachycardia, asystole, bradycardia, pulseless electrical activity, noncardiac mechanical factors (e.g., pulmonary embolism). | | Sudden cardiac death | Sudden unexpected death attributed to cardiac arrest, which occurs within 1 hour of symptom onset. | In unwitnessed cases, the definition is often expanded to include unexpected deaths where the subject was documented to be well within the preceding 24 hours. | Same as cardiac arrest. |
EPIDEMIOLOGY¶
• Impact: SCA and SCD are major public health problems; they account for 15% of all deaths and comprise 50% of all cardiac deaths. • Scale: In the US, there are ~350,000 EMS-attended out-of-hospital cardiac arrests and 210,000 SCDs in the adult population annually. • Demographics: ◦ Age: Rare in individuals <35 years (1–3 per 100,000); increases markedly with age as CAD and heart failure prevalence rise. ◦ Gender: Women have lower incidence of SCD/SCA; more likely to present with pulseless electrical activity (PEA) and occur at home. ◦ Race: Black Americans have higher rates of SCD, more unwitnessed arrests, and are more likely to be found with PEA, with lower survival rates. ◦ Geography: Rates are lower in Asia (52.5 per 100,000) than Europe (86.4), North America (98.1), or Australia (111.9). • Special Populations: ◦ Dialysis Patients: Absolute risk with annual rates approaching 5.5%. ◦ Dietary Factors: Higher intake of polyunsaturated fatty acids (n-3) and Mediterranean-style diets are associated with lower SCD risks; heavy alcohol intake (>3 drinks/day) increases risk.
Risk Factors¶
• Primary Cardiac: Preexisting CHD and HF are the most prevalent, associated with a 4- to 10-fold increase in SCD risk. • Systemic Factors: Hypertension, diabetes, hypercholesterolemia, obesity, and smoking. ◦ Diabetes: Particularly strong risk factor even in patients with established CHD. ◦ Hypertension/LVH: Especially important markers of SCD risk in blacks. • Other Risks: Obstructive sleep apnea, seizure disorders, and chronic kidney disease. • Genetic Component: A history of SCD in a first-degree relative is associated with increased risk for SCD and VF during acute MI (not necessarily increased risk for acute MI).
Precipitating Factors¶
• Temporal/Seasonal: Circadian peaks in morning and late afternoon; seasonal peaks in winter (Northern Hemisphere) or summer (Southern Hemisphere). • Situational: Clustering near transit hubs (trains, airports); higher risk in urban areas and near major roads. • Physical Exertion: Acute peak during or shortly after vigorous exertion; men are more susceptible. • Mechanism: Likely linked to heightened autonomic tone, which promotes ischemia and lowers the threshold for sustained VF.
ETIOLOGY & PATHOPHYSIOLOGY¶
• Primary Cause: Coronary artery disease (CAD) is the most common cause of SCD. ◦ White men: ~70% due to CAD. ◦ Women/Blacks: 40–50% due to CAD. • Non-ischemic Causes: Second most frequent; includes hypertrophic, dilated, and infiltrative cardiomyopathies. • Age-Specific Etiologies: ◦ <35 years: HCM, coronary artery anomalies, myocarditis, ARVC, and primary ion channelopathies (e.g., Long QT, Brugada). ◦ >35 years: Predominantly CAD and Valvular Heart Disease. • Rhythm Evolution: ◦ Historical: ~50% of victims found in VF. ◦ Modern: 20–25% found in VF; PEA and asystole are now more common due to aging, end-stage disease, and use of beta blockers/ICDs.
Pathophysiological Mechanisms¶
• CAD Mechanism: Acute myocardial ischemia/infarction → polymorphic VT/VF; also bradyarrhythmias (heart block) or PEA (myocardial rupture). • Scar-Mediated: Ventricular scar from prior infarcts or surgical repairs (e.g., VSD repair in Tetralogy of Fallot) → reentrant VT → VF. • Structural/Electrical Factors: LVH, ventricular stretch (fluid overload), and ion channel alterations lead to electrical heterogeneity. • Non-Cardiac Triggers: Pulmonary embolism, exsanguination, or respiratory arrest → PEA.
Table 317-2: Causes of Cardiovascular Collapse¶
• Coronary artery disease: (Substrates: Ischemia, rupture, tamponade) → Polymorphic VT/VF, Bradyarrhythmia, PEA, VT, VF. • Congenital heart disease: (Substrates: Surgical scar, Hypertrophy) → VT, Bradyarrhythmias, Polymorphic VT/VF. • Mitral valve prolapse/regurgitation: (Substrates: Pump failure, Ventricular scar) → Polymorphic VT/VF. • Wolff-Parkinson-White syndrome: (Substrate: Accessory connection) → Pre-excited AF/VF. • Noncardiac Causes: ◦ Pulmonary embolism → PEA ◦ Aortic dissection → PEA, VF ◦ Tension pneumothorax → PEA ◦ Neurogenic → PEA, bradyarrhythmia
CLINICAL FEATURES¶
• Syncope: Occurs when effective circulation is restored spontaneously (e.g., neurocardiogenic syncope). • Cardiac Arrest: Occurs when there is no spontaneous resolution of the underlying cause (e.g., severe bradycardia, myocardial rupture, pulmonary embolism).
Presentation¶
• Benign Conditions: e.g., neurocardiogenic syncope. • Life-threatening Conditions: Ventricular tachyarrhythmias, severe bradycardia, myocardial rupture (with tamponade), pulmonary embolism.
DIFFERENTIAL DIAGNOSIS¶
• Cardiac vs. Noncardiac: ◦ Cardiac: Arrhythmia, myocardial/valvular dysfunction, loss of vascular tone. ◦ Non-cardiac: Pulmonary embolism, stroke, aortic dissection, exsanguination (hypovolemia), tension pneumothorax, sepsis, neurogenic shock, drug overdose.
DIAGNOSTIC APPROACH¶
- Initial Assessment: Determine presence of pulse and identify rhythm.
- Rhythm Classification: ◦ Shockable: Polymorphic VT/VF, Monomorphic VT, Sinusoidal VT. ◦ Non-shockable: Asystole, Pulseless Electrical Activity (PEA).
- Identify Reversible Causes (H's and T's): • Hypoxia • Hypovolemia • Hydrogen ions (acidosis) • Hyperkalemia/Hypokalemia • Hypothermia • Tension pneumothorax • Tamponade • Toxins • Thrombosis (PE/MI)
Flowchart 1: Management of Cardiac Arrest¶
Pathway A: Shockable Rhythms (Polymorphic VT/VF, Monomorphic VT, Sinusoidal VT) 1. Initial Action: Chest compressions (100–120/min) + immediate defibrillation + CPR for ≥ 2 min. 2. No Shock Delivered: Continue compressions → initiate IV/IO access → advanced airway management. 3. Drug Administration: Epinephrine 1 mg IV every 3–5 min. 4. Second Decision (No Shock): Administer amiodarone 150 mg (initial) / 100 mg (repeat). 5. Specific Rhythm Actions: ◦ Polymorphic VT/VF → Immediate defibrillation. ◦ Monomorphic VT → Defibrillation; if no response, consider amiodarone. ◦ Sinusoidal VT → Defibrillation; if no response, consider amiodarone.
Pathway B: Non-shockable Rhythms (Asystole, PEA) 1. Initial Action: CPR, no-shock, IV/IO access. 2. Assessment: Confirm Asystole or assess pulse for PEA. 3. Pharmacology: ◦ Epinephrine 1 mg IV. ◦ Atropine 1 mg IV (for Bradycardia) + transvenous pacing. 4. Reversible Causes: Identify and treat H's and T's (Hypoxia, Hyper-/hypokalemia, Acidosis, etc.). 5. Defibrillation: Only if rhythm is shockable; otherwise focus on CPR and identifying causes.
MANAGEMENT & TREATMENT¶
- Immediate Resuscitation (Shockable): • Chest compressions at 100–120/min. • Defibrillation for Polymorphic VT/VF, Monomorphic VT, or Sinusoidal VT. • Epinephrine 1 mg IV every 3–5 min. • Amiodarone 150 mg (initial) / 100 mg (repeat).
- Immediate Resuscitation (Non-shockable): • CPR and IV/IO access. • Epinephrine 1 mg IV. • Atropine 1 mg IV or transvenous pacing for bradycardic rhythms.
- Treatment of Reversible Causes: • Address Hypoxia, Hypovolemia, Acidosis, Hyper-/hypokalemia, Hypothermia, Tension pneumothorax, Tamponade, Toxins, and Thrombosis (PE/MI).
- Post-Cardiac Arrest Care: • Targeted temperature management: 32–37.5°C for ≥ 24 hours.
- Device Therapy (ICD): • Primary Prevention Indications: ◦ NSVT or abnormal blood pressure response during exercise without other risk factors (Class IIb). ◦ HCM Risk-SCD ≥ 6% (Class IIa). ◦ HCM Risk-SCD 4–6% + specific features (LGE, LVEF <50%, etc.) (Class IIa/IIb). ◦ CPVT. ◦ Syncope during β-blocker treatment (Class I). • Contraindications for ICD: ◦ No expected survival or functional status for ≥ 1 year. ◦ Incessant VT or VF. ◦ Significant psychiatric illness. ◦ Drug-refractory NYHA Class IV heart failure (not candidates for transplant/resync). ◦ Syncope of undetermined cause in patient without inducible VT and no structural heart disease. ◦ VT/VF amenable to ablation in patients without other risk factors. ◦ Reversible disorders (electrolyte, drugs, trauma) in absence of structural heart disease.
Table 3: ICD Indications¶
• NSVT or abnormal BP response during exercise: Class IIb (AHA). • HCM Risk-SCD ≥ 6%: Class IIa (ESC & AHA). • HCM Risk-SCD 4–6% + LVEF <50% or Significant LGE or Ventricular Apical Aneurysm: Class IIa (ESC), Class IIb (AHA). • CPVT: Included in standard indications. • Syncope during β-blocker treatment: Class I (AHA).
Table 4: ICD Not Indicated¶
• No expected survival with acceptable functional status for ≥ 1 year. • Incessant VT or VF. • Significant psychiatric illnesses that may be aggravated by device. • Drug-refractory NYHA Class IV heart failure (not candidates for transplant/resync). • Syncope of undetermined cause in patient without inducible VT and no structural heart disease. • VT or VF amenable to ablation in patients without other risk factors (e.g., WPW, RV/LV outflow tract VT, idiopathic VT). • Reversible disorders (electrolyte imbalance, drugs, trauma) in absence of structural heart disease.
PROGNOSIS & COMPLICATIONS¶
• Survival: Fewer than 10% of out-of-hospital cardiac arrest victims survive to hospital discharge. • Post-Resuscitation: Targeted temperature management (32–37.5°C) for ≥ 24 hours is standard for comatose patients post-ROSC.
SPECIAL CONSIDERATIONS¶
• Pediatric/Young Adult (<35): Higher risk from genetic conditions (CPVT, HCM, ARVC) and primary ion channelopathies. • Elderly/Chronic Disease: Higher incidence of PEA due to end-stage cardiovascular disease and multi-organ failure.
KEY PEARLS & CLINICAL TRAPS¶
• H's and T's are the standard mnemonic for identifying reversible causes in cardiac arrest. • SCD is a major public health problem, accounting for 50% of all cardiac deaths. • ICD selection depends on both the presence of high-risk features (LVEF, LGE) and the absence of contraindications (incessant VT, poor prognosis). • Initial rhythm at scene is a key indicator of potential cause and prognosis; however, it may not reflect the initial precipitating event.
Reference Tables¶
TABLE 317-1 Distinction Between Cardiovascular Collapse, Cardiac Arrest, and Death TERM Cardiovascular collapse¶
Harrison's 22e, p.2333
| TERM | DEFINITION | QUALIFIERS | MECHANISMS |
|---|---|---|---|
| Cardiovascular collapse | Sudden loss of effective circulation due to cardiac and/or peripheral vascular factors that may reverse spontaneously (e.g., neurocardiogenic syncope transient hypotension) or require interventions (e.g., hypovolemia, tamponade, ventricular fibrillation). |
Broad term that includes cardiac arrest as well as transient events that characteristically revert spontaneously presenting as syncope. |
Same as cardiac arrest, plus neurocardiogenic syncope or other causes of transient loss of blood flow. |
| Abrupt cessation of cardiac function resulting in loss of effective circulation that may be reversible by prompt emergency medical intervention. |
Rare spontaneous reversions; likelihood of successful intervention relates to mechanism of arrest, clinical setting, availability of emergency medical services, and prompt return of circulation. |
||
| Sudden cardiac death | Sudden unexpected death attributed to cardiac arrest, which occurs within 1 hour of symptom onset. |
In unwitnessed cases, the definition is often expanded to include unexpected deaths where the subject was documented to be well within the preceding 24 hours. |
Same as cardiac arrest. |
TABLE 317-2 Causes of Cardiovascular Collapse and Sudden Cardiac Arrest CAUSE Cardiac Causes Coronary artery disease¶
Harrison's 22e, p.2335
| CAUSE | PATHOPHYSIOLOGIC SUBSTRATE | RHYTHM PRESENTATION |
|---|---|---|
| Cardiac Causes | ||
| Coronary artery disease Atherosclerotic, coronary spasm, congenital anomalies |
Acute myocardial ischemia/infarction, ventricular rupture, tamponade Ventricular scar from healed infarction |
Polymorphic VT/VF Bradyarrhythmia Pulseless electrical activity VT VF |
| Ventricular scar Ventricular hypertrophy Pump failure |
||
| Congenital heart disease (Tetralogy of Fallot, VSD, others) |
Ventricular scar from surgical repair Hypertrophy |
VT Bradyarrhythmias Polymorphic VT/VF |
| Obstruction to aortic outflow Ventricular hypertrophy |
||
| Mitral valve prolapse/mitral regurgitation | Pump failure Ventricular scar |
Polymorphic VT/VF |
| Abnormal cellular electrophysiology | ||
| Wolff-Parkinson-White syndrome | Accessory atrioventricular connection | Pre-excited AF/VF |
| Blunt precordial impact | ||
| Noncardiac Causes of Cardiovascular Collapse | ||
| Pulmonary embolism | PEA | |
| Aortic dissection | PEA, VF | |
| Tension pneumothorax | PEA | |
| Neurogenic | PEA, bradyarrhythmia |
TABLE 317-3 Implantable Cardioverter Defibrillator (ICD) Indications NSVT or abnormal blood pressure response during…¶
Harrison's 22e, p.2340
| ESC GUIDELINES | AHA/ACC/HRS GUIDELINES |
LEVEL OF EVIDENCE |
|
|---|---|---|---|
| NSVT or abnormal blood pressure response during exercise without additional SCD risk modifiers or high-risk features |
– | Class IIb | C |
| Estimated 5-year risk of sudden death based on the HCM Risk–SCD Calculator ≥6% | Class IIa | – | B |
| Estimated 5-year risk of sudden death based on HCM Risk–SCD Calculator (≥4 to <6%) AND | Class IIa | – | B |
| Significant LGE on CMR or | |||
| LVEF <50% or | |||
| Abnormal blood pressure during exercise test or | |||
| Left ventricular apical aneurysm or | |||
| Presence of sarcomeric pathogenic mutation | |||
| Estimated 5-year risk of sudden death based on the HCM Risk–SCD Calculator ≥4 to <6% | Class IIb | – | B |
| Estimated 5-year risk of sudden death based on the HCM Risk–SCD Calculator <4% AND | Class IIb | – | B |
| Significant LGE on CMR or | |||
| LVEF <50% or | |||
| Left ventricular apical aneurysm | |||
| – Class I Class IIa – Class IIb |
Class I – – Class IIb – |
||
| Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) | |||
| Syncope during β-blocker treatment | – | Class I | C |
| Syncope during combined β-blocker and flecainide treatment | Class IIa | – | C |
| Class IIa Class IIb |
Class I – |
||
| Cardiac Sarcoidosis | |||
| Cardiac sarcoidosis with 1 or more risk factors for SCD | – | Class IIa | C |
| Indication for permanent pacemaker implantation regardless of LVEF | Class IIa | – | C |
| LVEF >35% and significant LGE on CMR after resolution of acute inflammation | Class IIa | – | C |
| LVEF 35–50% and inducible VT at PES | Class IIa | – | C |
| – | Class IIb | ||
| Left Ventricular Noncompaction | |||
| Patients with left ventricular noncompaction | – | Class IIb | C |
TABLE 317-4 Implantable Cardioverter Defibrillator (ICD) Not Indicated Patients who do not have a reasonable…¶
Harrison's 22e, p.2341
| Patients who do not have a reasonable expectation of survival with an acceptable functional status for at least 1 year, even if they meet ICD implantation criteria. |
||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Patients with incessant VT or VF. | ||||||||||||||||
| Patients with significant psychiatric illnesses that may be aggravated by device implantation or that may preclude systematic follow-up. |
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| Patients with drug-refractory New York Heart Association class IV congestive heart failure who are not candidates for cardiac transplantation or cardiac resynchronization therapy. |
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| Syncope of undetermined cause in a patient without inducible ventricular tachyarrhythmias and without structural heart disease. |
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| VF or VT is amenable to surgical or catheter ablation in patients without other disease predisposing to sudden cardiac arrest (e.g., atrial arrhythmias associated with Wolff-Parkinson-White syndrome, RV or LV outflow tract VT, idiopathic VT, or fascicular VT in the absence of structural heart disease). |
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| Patients with ventricular tachyarrhythmias due to a completely reversible disorder in the absence of structural heart disease (e.g., electrolyte imbalance, drugs, or trauma). |
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| Post-MI, CHD, CM, or HF with LVEF>35% |
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| No known heart disease 50% |
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| Absolute Risk of Sudden Cardiac Death by Clinical Subgroups 7.2% 6.0% |
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| 3.0% | ||||||||||||||||
| 1.5% 1.5% 1.0% 0.8% 0.08% |