Disorders Revealed by the Cardiac Exam

Must know

• Tricyclic Antidepressant (TCA) Cardiac RisksSource Scope Note: Fitzgerald Chapter 18 is not included in the provided notebook files (which cover Chapters 1 through 16), but tricyclic antidepressant (TCA) cardiac risks are extensively detailed in Fitzgerald Chapters 2, 8, and 9.

  • Source Scope Note: Fitzgerald Chapter 18 is not included in the provided notebook files (which cover Chapters 1 through 16), but tricyclic antidepressant (TCA) cardiac risks are extensively detailed in Fitzgerald Chapters 2, 8, and 9.
  • Baseline ECG Mandate: Obtaining a baseline electrocardiogram (ECG) is mandatory before starting a tricyclic antidepressant (TCA) such as amitriptyline, nortriptyline, imipramine, or desipramine, particularly in patients over age 40 or those with personal or family cardiac history.
  • Electrophysiological Mechanism: TCAs exert quinidine-like Class IA antiarrhythmic actions and block fast sodium channels, slowing cardiac conduction velocity and prolonging PR, QRS, and QTc intervals.
  • QRS Duration Thresholds: A QRS duration exceeding 100 milliseconds indicates an elevated risk for seizures, while a QRS duration exceeding 160 milliseconds predicts a high risk for lethal ventricular arrhythmias, including ventricular tachycardia and torsades de pointes.
  • Absolute Contraindications: Recent myocardial infarction, acute post-MI recovery phase, second-degree or third-degree heart block, severe bundle branch block, or existing baseline QTc prolongation are strict contraindications to TCA therapy.
  • Autonomic Cardiac Effects: Alpha-1 adrenergic receptor blockade by TCAs causes significant orthostatic hypotension and reflex tachycardia, while muscarinic anticholinergic blockade causes persistent sinus tachycardia.
• Electrophysiology and Conduction BlockadeObtaining a baseline 12-lead ECG prior to prescribing is the mandatory first-line safety step.

  • What it is: TCAs inhibit cardiac fast sodium channels (Class IA antiarrhythmic effect) and delayed rectifier potassium channels, delaying cardiac depolarization and repolarization.
  • Why boards care: TCA cardiotoxicity is a leading cause of fatal drug overdose in psychiatric practice.
  • Normal QRS is less than 100 milliseconds. QRS between 100 and 160 milliseconds indicates moderate toxicity. QRS greater than 160 milliseconds indicates severe toxicity.
  • Typical board clue: A depressed patient presenting after an ingestion with confusion, dry mouth, dilated pupils, hypotension, and a widened QRS complex on ECG.
  • Obtaining a baseline 12-lead ECG prior to prescribing is the mandatory first-line safety step.
  • When the answer changes: If the stem describes an acute overdose with QRS widening greater than 100 milliseconds, the first-line intervention changes to immediate intravenous sodium bicarbonate administration to alkalinize the serum and unbind the drug from sodium channels.

  Safety. Never prescribe TCAs to patients with active suicidal ideation or a history of serious suicide attempts due to extreme lethality in overdose.

• Autonomic Cardiac Adverse EffectsAlpha-1 Adrenergic Blockade: Causes peripheral vasodilation leading to orthostatic hypotension, dizziness, and reflex tachycardia. This is particularly dangerous in older adults due to elevated fall and fracture risks.

  • Alpha-1 Adrenergic Blockade: Causes peripheral vasodilation leading to orthostatic hypotension, dizziness, and reflex tachycardia. This is particularly dangerous in older adults due to elevated fall and fracture risks.
  • Muscarinic Anticholinergic Blockade: Inhibits vagal tone, causing persistent sinus tachycardia.
  • Mistaking TCA induced sinus tachycardia or orthostatic dizziness for worsening anxiety or panic disorder, leading to inappropriate dose escalation instead of discontinuation.

  Board trap. Mistaking TCA induced sinus tachycardia or orthostatic dizziness for worsening anxiety or panic disorder, leading to inappropriate dose escalation instead of discontinuation.

• TCAs vs. SSRIs Cardiac Safety ProfileThink TCAs: Quinidine-like sodium channel blockade, significant conduction delays, high risk of fatal arrhythmias in overdose, mandatory baseline ECG.

  • Think TCAs: Quinidine-like sodium channel blockade, significant conduction delays, high risk of fatal arrhythmias in overdose, mandatory baseline ECG.
  • Think SSRIs: Favorable overall cardiovascular safety profile, minimal conduction interference, safe in mild overdose. (Note: citalopram requires dose capping at 20 mg daily in patients over age 60 due to dose-dependent QTc prolongation).
  • Priority difference: TCAs require pre-treatment cardiac screening and strict toxicity monitoring. SSRIs are the preferred first-line choice for patients with comorbid cardiovascular disease.
  • What boards are really testing: Selecting cardiosafe antidepressant agents in patients with pre-existing heart disease or elevated suicide risk.
• QRS Interval Risk Tiers in TCA ToxicityQRS less than 100 ms: Normal cardiac conduction; low risk of acute life-threatening arrhythmia.

  • QRS less than 100 ms: Normal cardiac conduction; low risk of acute life-threatening arrhythmia.
  • QRS 100 to 160 ms: Moderate toxicity; significantly increased risk for grand mal seizures.
  • QRS greater than 160 ms: Severe cardiotoxicity; high risk for ventricular tachycardia, torsades de pointes, and cardiovascular collapse.
  • What boards are really testing: Identifying QRS width as the key diagnostic and prognostic marker driving emergency therapy in TCA overdose.
• Common Board TrapsThe Youth Assumption Trap: Assuming a young or physically active patient with depression does not require a baseline ECG before starting a TCA. National standards require baseline cardiac screening regardless of age when initiating cardiotoxic agents.

  • The Youth Assumption Trap: Assuming a young or physically active patient with depression does not require a baseline ECG before starting a TCA. National standards require baseline cardiac screening regardless of age when initiating cardiotoxic agents.
  • The Refractory Escalation Trap: Escalating the dose of amitriptyline or imipramine when a patient reports persistent palpitations or dizziness. These are direct toxic anticholinergic and alpha-blockade side effects, not undertreated anxiety.
  • Choosing Dialysis in Toxicity: Selecting hemodialysis or hemoperfusion for acute TCA overdose. TCAs are highly protein-bound with a large volume of distribution, making dialysis ineffective. The correct emergency treatment is intravenous sodium bicarbonate.
• Active Recall Checkpoints1. What baseline diagnostic test must be performed before starting any patient on a tricyclic antidepressant?

  • 1. What baseline diagnostic test must be performed before starting any patient on a tricyclic antidepressant?
  • 2. What QRS duration threshold on an ECG indicates a high risk for seizures in TCA overdose?
  • 3. What QRS duration threshold indicates a high risk for life-threatening ventricular arrhythmias in TCA overdose?
  • 4. What receptor blockade is responsible for TCA induced orthostatic hypotension?
  • 5. What is the emergency pharmacological treatment of choice for TCA induced cardiotoxicity and QRS prolongation?
• Lithium Cardiac ImpactsObtain baseline ECG, serum creatinine, eGFR, BUN, TSH, and serum hCG prior to initiating lithium therapy.

  • Obtain baseline ECG, serum creatinine, eGFR, BUN, TSH, and serum hCG prior to initiating lithium therapy.
  • Lithium induces benign, reversible T-wave flattening or T-wave inversion on ECG in up to 30 percent of patients at therapeutic doses.
  • Lithium depresses sinus node automaticity, creating risks for sinus bradycardia, sinoatrial block, or AV block in susceptible individuals.
  • First-trimester pregnancy exposure to lithium increases the risk of Ebstein anomaly, a severe congenital tricuspid valve malformation.
  • Therapeutic serum levels range from 0.6 to 1.2 mEq/L for maintenance, while levels at or above 1.5 mEq/L cause toxic cardiac and neurological manifestations.
  • Adjusting lithium dosing in an established diagnosis of bipolar disorder is classified as tertiary prevention.
• Safety AlertFirst-trimester pregnancy exposure to lithium carries a high-yield board risk for Ebstein anomaly, characterized by downward displacement of the tricuspid valve into the right ventricle and right atrial enlargement.

  • First-trimester pregnancy exposure to lithium carries a high-yield board risk for Ebstein anomaly, characterized by downward displacement of the tricuspid valve into the right ventricle and right atrial enlargement.
  • Severe toxicity with a serum level at or above 1.5 to 2.0 mEq/L can trigger sinus node arrest, severe bradycardia, ventricular arrhythmias, and profound neurological collapse.
• Board TrapMistaking benign T-wave flattening or inversion on ECG for acute myocardial ischemia, leading to unnecessary emergency referrals or premature discontinuation of lithium.

  • Mistaking benign T-wave flattening or inversion on ECG for acute myocardial ischemia, leading to unnecessary emergency referrals or premature discontinuation of lithium.
  • Failing to order a baseline ECG before prescribing lithium, which misses pre-existing sick sinus syndrome or conduction blocks.
• First-LineLithium remains a first-line mood stabilizer for acute mania and maintenance in bipolar I disorder, provided baseline cardiac, renal, thyroid, and pregnancy screening is completed first.

  • Lithium remains a first-line mood stabilizer for acute mania and maintenance in bipolar I disorder, provided baseline cardiac, renal, thyroid, and pregnancy screening is completed first.
• Cardiac Findings and Laboratory Workup SynthesisBaseline cardiac and metabolic evaluation: Before starting lithium, order an ECG to evaluate baseline rhythm and conduction, along with renal function tests (eGFR and creatinine), thyroid panel (TSH), serum electrolytes, and pregnancy test (hCG).

  • Baseline cardiac and metabolic evaluation: Before starting lithium, order an ECG to evaluate baseline rhythm and conduction, along with renal function tests (eGFR and creatinine), thyroid panel (TSH), serum electrolytes, and pregnancy test (hCG).
  • Conduction effects: Lithium replaces intracellular potassium in cardiac myocytes, altering repolarization. This produces benign T-wave flattening or inversion on ECG, while depressing sinus node pacemaking function.
  • High-risk populations: Older adults and patients with underlying sick sinus syndrome or AV node disease face heightened risk for severe sinus bradycardia and sinoatrial block when taking lithium.
• Anorexia Nervosa Cardiovascular SignsAnorexia Nervosa causes severe, life-threatening cardiovascular complications due to starvation-induced myocardial atrophy, autonomic dysregulation, and electrolyte depletion.

  • Anorexia Nervosa causes severe, life-threatening cardiovascular complications due to starvation-induced myocardial atrophy, autonomic dysregulation, and electrolyte depletion.
  • Cardinal cardiovascular signs include sinus bradycardia with a resting heart rate below 50 beats per minute, hypotension with blood pressure below 90/60 mmHg, and QTc prolongation on ECG.
  • Functional mitral valve prolapse occurs in up to 30 percent to 60 percent of severe cases due to a disproportion between a shrunken left ventricle and normal valve leaflet size.
  • Electrolyte derangements, specifically hypokalemia and hypomagnesemia from starvation or purging, drive QTc prolongation and fatal ventricular arrhythmias like Torsades de Pointes.
  • Immediate medical hospitalization is indicated when resting heart rate drops below 40 beats per minute, blood pressure drops below 90/60 mmHg, temperature falls below 36 degrees Celsius (96.8 degrees Fahrenheit), or QTc interval exceeds 450 milliseconds.
  • Bupropion is strictly contraindicated in eating disorders due to an elevated risk of drug-induced seizures.
• High-Yield Clinical TeachingPathophysiology of Myocardial Atrophy

  • Pathophysiology of Myocardial Atrophy
  • Autonomic Dysregulation and Vital Sign Depression
  • Electrophysiological Instability
  • Functional Valvular Changes
• Spoken Review of Cardiac Findings and MonitoringOutpatient management is appropriate when resting heart rate remains above 50 beats per minute, systolic blood pressure stays above 90/60 mmHg, and body weight is above 85 percent of ideal body weight.

  • Outpatient management is appropriate when resting heart rate remains above 50 beats per minute, systolic blood pressure stays above 90/60 mmHg, and body weight is above 85 percent of ideal body weight.
  • Immediate inpatient medical hospitalization is required when resting heart rate drops below 40 beats per minute, systolic blood pressure drops below 90 mmHg, QTc interval exceeds 450 milliseconds, or body weight falls below 75 percent of ideal body weight (or BMI is below 15).
• Bulimia Nervosa Cardiac ComplicationsBaseline ECG, eGFR, serum creatinine, and TSH are required prior to initiating lithium therapy.

  • ANCC and AANPCB board exams evaluate cardiovascular and body system considerations across all domains, representing up to 22% of scientific foundation items.
  • Baseline ECG, eGFR, serum creatinine, and TSH are required prior to initiating lithium therapy.
  • Citalopram is capped at a maximum daily dose of 20 mg in adults aged 60 and older due to dose-dependent QTc prolongation risk.
  • Clozapine carries FDA black box warnings for myocarditis and cardiomyopathy, requiring immediate drug cessation if dyspnea, fever, chest pain, or palpitations develop.
  • Tricyclic antidepressants require baseline ECG and ongoing monitoring because overdose carries a high risk of fatal ventricular arrhythmias and heart block.
  • Do not diagnose a primary anxiety or panic disorder without first ruling out medical cardiovascular mimics such as myocardial infarction, pulmonary embolism, or pheochromocytoma.

  Board trap. Tricyclic antidepressants require baseline ECG and ongoing monitoring because overdose carries a high risk of fatal ventricular arrhythmias and heart block.

  Safety. ANCC and AANPCB board exams evaluate cardiovascular and body system considerations across all domains, representing up to 22% of scientific foundation items.