Cardiovascular Collapse, Cardiac Arrest, and Sudden Cardiac Death¶
Chapter 317 | Part 8: Critical Care Medicine
KEY CLINICAL POINTS¶
- Cardiovascular collapse is severe hypotension from acute cardiac dysfunction or peripheral vasculature failure, leading to cerebral hypoperfusion.
- Sudden cardiac arrest (SCA) is abrupt loss of cardiac function, while sudden cardiac death (SCD) is unexpected death within 1 hour of symptom onset.
- ICD implantation is recommended for primary prevention in high-risk patients with structural heart disease, LVEF ≤ 35%, or genetic arrhythmia syndromes.
1. DEFINITION & OVERVIEW¶
Cardiovascular collapse refers to severe hypotension from acute cardiac dysfunction or loss of peripheral vasculature resistance, resulting in cerebral hypoperfusion and loss of consciousness. Cardiac arrest is abrupt cessation of cardiac function, while sudden cardiac death (SCD) is unexpected death due 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 | Broad term including cardiac arrest and transient events | 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 | Rare spontaneous reversions; likelihood of successful intervention relates to mechanism of arrest | Ventricular fibrillation, ventricular tachycardia, asystole, pulseless electrical activity |
| Sudden cardiac death | Sudden unexpected death attributed to cardiac arrest | In unwitnessed cases, definition expanded to include unexpected deaths where subject was documented well within 24 hours | Same as cardiac arrest |
1.1 Cardiovascular Collapse vs. Cardiac Arrest vs. SCD¶
Cardiovascular collapse includes transient events like neurocardiogenic syncope or reversible causes like hypovolemia. Cardiac arrest is abrupt cessation of cardiac function, with VF/VT being the most common rhythm. SCD is defined as unexpected death due to cardiac arrest, often with no witnessed collapse.
1.2 Mechanisms of Collapse¶
Collapse can result from cardiac arrhythmias (VF, VT), severe myocardial dysfunction, loss of vascular tone, or acute venous return disruption. Neurocardiogenic syncope and transient hypotension may resolve spontaneously.
2. EPIDEMIOLOGY¶
SCA and SCD are major public health issues, accounting for 15% of all deaths. In the U.S., ~350,000 out-of-hospital cardiac arrests and 210,000 SCDs occur annually. Rates vary by age, gender, and race, with higher incidence in Black Americans and lower in Asians.
Table 317-2: Causes of Cardiovascular Collapse and Sudden Cardiac Arrest¶
| CAUSE | PATHOPHYSIOLOGIC SUBSTRATE | RHYTHM PRESENTATION |
|---|---|---|
| Coronary artery disease | Acute myocardial ischemia/infarction, ventricular rupture, tamponade | Polymorphic VT/VF, Bradyarrhythmia, Pulseless electrical activity |
| Cardiomyopathies | Ventricular scar, ventricular hypertrophy, pump failure | Polymorphic VT/VF, Bradyarrhythmia, Pulseless electrical activity |
| Arrhythmia syndromes | Abnormal cellular electrophysiology | Polymorphic VT/VF |
| Noncardiac causes | Pulmonary embolism, stroke, aortic dissection | PEA, bradyarrhythmia, VF |
2.1 Demographics¶
SCD rates increase with age, peaking in individuals >65 years. Women have lower incidence than men, with higher PEA presentation. Black Americans have higher SCD rates and lower survival compared to white Americans.
2.2 Risk Factors¶
Prevalent risk factors include hypertension, diabetes, hypercholesterolemia, smoking, and family history of SCD. CAD accounts for ~70% of SCD in white men but only 40–50% in women and blacks.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
SCD is primarily due to CAD (70% in white men) or nonischemic cardiomyopathies. Mechanisms include ischemic VT/VF, severe bradyarrhythmias, and structural abnormalities like scar-mediated reentry. Genetic syndromes (e.g., Brugada, LQTS) and acquired factors (e.g., electrolyte imbalances) also contribute.
Table 313-1: Proportionate Causes of SCD¶
| CAUSE | PROPORTION |
|---|---|
| Coronary artery disease | 40–70% |
| Inherited arrhythmia syndromes | 1–2% in Western countries |
| Nonischemic cardiomyopathies | 10–15% in Western countries |
| Valvular heart disease | 1–5% |
| Myocarditis | 1–5% |
3.1 Cardiac Causes¶
Acute MI, ventricular scar, cardiomyopathies (HCM, ARVC), and arrhythmogenic substrates (e.g., scar-mediated reentry) are leading causes. Nonischemic cardiomyopathies account for 10–15% of SCD cases in Western countries.
3.2 Noncardiac Causes¶
Pulmonary embolism, stroke, aortic dissection, and hypovolemia can cause PEA. Neurogenic shock and drug toxicity (e.g., hyperkalemia) are also implicated.
4. CLINICAL FEATURES¶
Clinical presentation varies by cause. VF is the most common initial rhythm, but PEA and asystole are now more frequent. Symptoms include syncope, chest pain, and sudden collapse. Complications include brain injury, myocardial rupture, and cardiac tamponade.
4.1 Initial Rhythm¶
VF is most common in early post-MI, but PEA/asystole dominate in later stages. VF is more treatable than PEA, with survival rates up to 30% in some regions.
4.2 Neurological Outcomes¶
Neurological recovery decreases rapidly with time to ROSC. Therapeutic hypothermia (32–37.5°C) improves outcomes in patients with shockable rhythms.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses include neurocardiogenic syncope, pulmonary embolism, stroke, and hypovolemic shock. Unwitnessed arrests require exclusion of noncardiac causes like trauma or poisoning.
5.1 Unwitnessed Arrests¶
Assume cardiac cause unless noncardiac factors (e.g., trauma, poisoning) are confirmed. Autopsy is needed to exclude noncardiac causes in unwitnessed cases.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis relies on ECG, cardiac imaging, and autopsy. Key tests include ECG for VF/VT, echocardiography for structural heart disease, and cardiac MRI for scar detection. Autopsy is critical for unwitnessed arrests.
Table 317-3: ICD Indications¶
| CONDITION | AHA/ACC/HRS | ESC |
|---|---|---|
| LVEF £35% + NYHA II–III | Class I | Class I |
| LVEF £30% + NYHA I | Class I | Class IIa |
| Nonischemic CM with LVEF £35% | Class IIa | Class IIa |
| Arrhythmogenic RV dysplasia | Class IIa | Class IIa |
| Hypertrophic CM with LVEF >35% | Class IIa | Class IIa |
6.1 Diagnostic Criteria¶
SCD is diagnosed as unexpected death due to cardiac arrest within 1 hour of symptom onset. Unwitnessed arrests require exclusion of noncardiac causes.
7. MANAGEMENT & TREATMENT¶
Immediate CPR, defibrillation, and advanced life support are critical. Post-resuscitation care includes hypothermia, vasopressors, and ICD implantation for high-risk patients. Long-term management involves revascularization, beta-blockers, and lifestyle modifications.
Table 317-4: ICD Not Indicated¶
| INDICATION | DESCRIPTION |
|---|---|
| Incessant VT/VF | Continuous arrhythmia unresponsive to therapy |
| Psychiatric illness | Risk of device exacerbating mental health |
| Drug-refractory HF | Not candidates for transplant or CRT |
| Undetermined syncope | No inducible VT/VF or structural disease |
| Reversible causes | Electrolyte imbalance, drug toxicity, trauma |
7.1 Resuscitation Algorithm¶
Follow the 'chain of survival': early CPR, defibrillation, advanced life support, and post-arrest care. VF is treated with 200-J biphasic shocks, while PEA/asystole requires CPR and epinephrine.
7.2 Post-Arrest Care¶
Therapeutic hypothermia (32–37.5°C) improves neurological outcomes. Monitor for reinfarction, arrhythmias, and metabolic derangements. ICD implantation is recommended for secondary prevention in survivors.
8. PROGNOSIS & COMPLICATIONS¶
Survival rates vary by initial rhythm (VF > PEA/asystole). Complications include brain injury, myocardial rupture, and cardiac tamponade. Long-term risks include recurrent VT/VF and heart failure.
8.1 Survival Rates¶
Survival to hospital discharge is ~16% for out-of-hospital arrests. VF survivors have better outcomes than PEA/asystole. Neurological recovery is <30% at 5 minutes without CPR.
9. SPECIAL CONSIDERATIONS¶
Special populations include pregnant women, elderly, and athletes. Pregnancy requires careful management of arrhythmias and anticoagulation. Athletes with exertion-related SCD may benefit from ICDs.
9.1 Pregnancy¶
Cardiac arrest during pregnancy is rare but requires immediate resuscitation. ICDs may be contraindicated due to risk of fetal harm. Anticoagulation must balance maternal and fetal risks.
10. KEY POINTS & CLINICAL PEARLS¶
- VF is the most treatable rhythm in cardiac arrest. 2. ICDs are indicated for secondary prevention in survivors of SCA. 3. Therapeutic hypothermia improves neurological outcomes. 4. SCD risk is highest in patients with CAD, HCM, and genetic arrhythmias. 5. Early CPR and defibrillation are critical for survival.