Case Media – A Sinister Cause of Sudden Cardiac Death – University of Washington

A 40-year-old woman with a history of recurrent exertional syncope had sudden loss of consciousness while kissing her partner. The patient received bystander CPR while 911 was called. EMS arrived within 10 minutes of the call and found the patient apneic and unresponsive. Initial rhythm check showed narrow complex tachycardia at a rate of 136 BPM. ROSC was eventually achieved. A 12-lead ECG showed that the patient was in atrial fibrillation with rapid ventricular rate. The patient was intubated and brought to the emergency department. The patient spontaneously converted to sinus rhythm en route to the hospital.

In the emergency department, vital signs were remarkable for hypotension (76/64 mmHg) and sinus tachycardia (110 BPM). The physical exam was remarkable for an inability to follow commands. Laboratory data was remarkable for hypokalemia (2.5 mmol/L), transaminitis (AST 138 units/L, ALT 98 units/L), acidemia (pH 7.12), and hyperlactatemia (11.2 mmol/L). CT scan of the chest revealed a thin membrane within the left atrium. Transthoracic echocardiogram showed normal biventricular size and function, severe tricuspid regurgitation, pulmonary artery systolic pressure of 93 mmHg, and the presence of a membrane within the left atrium with a mean gradient of 25 mmHg between the proximal and distal left atrial chambers. Vasopressors and targeted temperature management were initiated.

The patient was able to be re-warmed with eventual discontinuation of vasopressors, however she had ongoing encephalopathy and seizures concerning for hypoxic brain injury. There was discussion with the adult congenital heart disease team about next steps in management, however the patient was too sick to undergo any definitive treatment for the intracardiac membrane within the left atrium. The patient developed ventilator associated pneumonia and antibiotics were initiated. The patient ultimately developed  bradycardia and pulseless electrical activity; ROSC was unable to be achieved, resulting in death.

Autopsy was remarkable for the presence of a fenestrated intracardiac membrane within the left atrium and lack of other apparent congenital heart defects. There was right ventricular hypertrophy and pulmonary artery intimal thickening with interstitial fibrosis suggestive of pulmonary hypertension. There were bilateral acute subsegmental pulmonary emboli present. The cause of death was declared to be arrhythmia in the setting of pulmonary hypertension and right sided heart failure caused by cor triatriatum sinistrum with a significant contribution from acute subsegmental pulmonary emboli.

Case Media – A Sinister Cause of Sudden Cardiac Death – University of Washington

Pearls – A Sinister Cause of Sudden Cardiac Death – University of Washington

1. In a patient presenting with syncope, the following feature may indicate an underlying cardiac etiology: exertional syncope, sudden syncope without a prodrome, structural heart disease, advanced age, and family history of sudden cardiac or unexplained death.
2. Cor triatriatum sinistrum is diagnosed by CT, echocardiography, or MRI and is often found incidentally in adults.  
3. Acute management of CTS is similar to mitral stenosis and consists of 1) careful volume management to avoid both hypovolemia and hypervolemia, and 2) avoidance of tachycardia to allow for adequate LV filling during diastole. Surgical resection of the membrane is definitive.
4. A mean gradient of ≥ 8 mmHg across a CTS membrane is hemodynamically significant and should prompt surgical evaluation for membrane resection.

Show Notes -A Sinister Cause of Sudden Cardiac Death – University of Washington

• Syncope
  • Loss of consciousness due to transient decrease in cerebral blood flow
  • Differential
    • Orthostatic
    • Neurally mediated
    • Cardiogenic
    • Mimickers of syncope: seizures, head trauma causing loss of consciousness, hypoglycemia
  • Red flag symptoms of cardiogenic syncope
    • Advanced age
    • Exertional or while lying down
    • Palpitations prior to event
    • Structural heart disease
    • Family history of unexplained or sudden cardiac death
  • Structural heart disease etiologies
    • Generally left sided and causes obstruction to blood flow
    • Valvular stenoses
    • Hypertrophic cardiomyopathy
    • Cardiac tumors
  • Arrhythmia etiologies
    • Can be caused by any brady- or tachyarrhythmia, especially in the setting of structural heart disease
    • Most commonly
      • Sinus node disease
      • High degree heart block
      • Ventricular arrhythmia

• Pulse pressure
  • Difference between systolic and diastolic pressure
  • Normal ~ 40 mmHg
  • Narrow – <25% of systolic blood pressure
  • Wide – >100 mmHg
  • Wide pulse pressure etiologies
    • Physical conditioning (normal variant)
    • Aortic regurgitation
    • Severe iron deficiency anemia
    • Hyperthyroidism
    • Arteriosclerosis
    • Shunting from arteriovenous fistulas
  • Narrow pulse pressure etiologies – indicates low stroke volume/cardiac output
    • Heart failure
    • Hypovolemia
    • Blood loss
    • Valvular stenosis
    • Cardiac tamponade
    • Pulmonary embolism

• Cor triatriatum sinister
  • Presence of a membrane within the left atrium that divides the left atrium into 2 chambers
  • Pathophysiology
    • Theorized to be caused by misincorporation of the pulmonary veins within the left atrium causing a membrane within the left atrium
    • If restrictive, sequelae include congestive heart failure, pulmonary hypertension, and right ventricular dysfunction
    • Often associated with other congenital heart disease (ASD, pulmonary venous return, mitral regurgitation)
  • Epidemiology
    • Among the rarest of all congenital heart disease (up to 0.4% of all congenital heart disease, but true incidence is unknown as many can be asymptomatic)
    • Found more often in infancy/childhood; often found incidentally in adults
  • Signs/symptoms
    • Many are asymptomatic
    • Over time, membrane may become fibrotic or calcified and cause significant obstruction
    • Infants/children – pulmonary congestion, respiratory infections, cyanosis, growth restriction
    • Adults – dyspnea, chest pain, palpitations, syncope
      • Thrombotic events are common likely from vascular injury and congestion/stasis
      • Atrial arrhythmia is associated with CTS, possibly from scarring of the membrane vs chronic elevation of left atrial pressure
  • Diagnosis
    • Made by imaging (CT chest/cardiac, echocardiography, MRI)
    • Primary competing differential diagnosis is supravalvular mitral ring
      • If intra-atrial membrane contains the left atrial appendage and pulmonary veins -> supravalvular mitral ring
        • Associated with Schone complex (supravalvular mitral ring, parachute mitral valve, subaortic stenosis, aortic coarctation
        • CTS rarely associated with Shone complex
      • If intra-atrial membrane contains only the pulmonary veins -> CTS
        • Can be found incidentally and cause technical issues in cardiac procedures that require transeptal atrial punctures
    • Quantify degree of restriction with echocardiography; gradients ≥ 8 mmHg are significant per AHA guidelines
  • Treatment
    • Acute:
      • Diuretics to treat congestion
      • Fluids to avoid hypovolemia due to preload dependence for cardiac output
      • Treat underlying causes of tachycardia to optimize diastolic filling
      • Treat tachyarrhythmia with anti-arrhythmis and AV nodal blockers
    • Chronic/definitive:
      • Surgical resection of the membrane offers a good and durable outcome
        • Low recurrence rate, residual gradients likely due to incomplete resection
• Pulmonary hypertension
  • WHO classification
    • Group 1 – Pulmonary arterial hypertension (idiopathic, toxin induced, HIV, connective tissue disease, congenital heart disease
      • Congenital heart disease comprises a small portion of group 1, typically from shunt lesions
    • Group 2 – Left sided heart disease
    • Group 3 – Pulmonary disease
    • Group 4 – CTEPH
    • Group 5 – Unclear mechanisms (sickle cell, sarcoid, metabolic disease)

References –

1. Albassam OT, Redelmeier RJ, Shadowitz S, Husain AM, Simel D, Etchells EE. Did This Patient Have Cardiac Syncope?: The Rational Clinical Examination Systematic Review. JAMA. 2019;321(24):2448-2457. doi:10.1001/jama.2019.8001
2. Jegier W, Gibbons JE, Wigglesworth FW. Cortriatriatum: clinical, hemodynamic and pathological studies surgical correction in early life. Pediatrics. 1963;31:255-267.
3. Jha AK, Makhija N. Cor Triatriatum: A Review. Semin Cardiothorac Vasc Anesth. 2017;21(2):178-185. doi:10.1177/1089253216680495
4. Rudienė V, Hjortshøj CMS, Glaveckaitė S, et al. Cor triatriatum sinistrum diagnosed in the adulthood: a systematic review. Heart. 2019;105(15):1197-1202. doi:10.1136/heartjnl-2019-314714
5. Saxena P, Burkhart HM, Schaff HV, Daly R, Joyce LD, Dearani JA. Surgical repair of cor triatriatum sinister: the Mayo Clinic 50-year experience. Ann Thorac Surg. 2014;97(5):1659-1663. doi:10.1016/j.athoracsur.2013.12.046
6. Stout KK, Daniels CJ, Aboulhosn JA, et al. 2018 AHA/ACC Guideline for the Management of Adults With Congenital Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines [published correction appears in J Am Coll Cardiol. 2019 May 14;73(18):2361]. J Am Coll Cardiol. 2019;73(12):1494-1563. doi:10.1016/j.jacc.2018.08.1028
7. Yaroglu Kazanci S, Emani S, McElhinney DB. Outcome after repair of cor triatriatum. Am J Cardiol. 2012;109(3):412-416. doi:10.1016/j.amjcard.2011.09.029