General anesthesia and septal bulge : management and pre-anesthetic evaluation

Recently, I encountered a patient with hypertrophic cardiomyopathy during an anesthesia consultation for planned digestive surgery. With the assistance of a more experienced colleague, we were able to plan a comprehensive preoperative assessment.

The septal bulge, corresponding to an asymmetric septal hypertrophy, is a common anatomical feature associated with obstructive hypertrophic cardiomyopathy (HOCM). This condition can lead to dynamic left ventricular outflow tract (LVOT) obstruction, increasing the risk of perioperative complications under general anesthesia (GA). This article outlines the anesthetic risks related to this pathology and the necessary pre-anesthetic consultation (PAC) evaluations.

1. Impact of septal bulge on general anesthesia

Septal bulge is not an absolute contraindication for a GA, but it exposes the patient to several risks due to the hemodynamic alterations it induces.

1.1. Mechanisms of decompensation under GA

- Excessive vasodilation → Reduced afterload → Increased LVOT gradient.

- Hypovolemia → Decreased preload → Cardiac output collapse.

- Tachycardia → Reduced diastolic filling time → Exacerbation of obstruction.

- Positive inotropic effects (ketamine, catecholamines) → Worsening obstruction.

- Excessive bradycardia → Risk of myocardial ischemia due to blood stasis.

1.2. Anesthetic precautions

- Stabilization of heart rate (60-80 bpm) with possible beta-blocker therapy.

- Optimization of intravascular volume with tailored fluid management.

- Limiting excessive vasodilation, favoring agents with minimal vasodilatory effects (e.g., etomidate for the induction).

- Use of norepinephrine rather than ephedrine for hypotension management.

- Invasive monitoring (arterial line, possible right heart catheterization depending on risk assessment).

2. Pre-anesthetic consultation (PAC) evaluations

A thorough cardiologic assessment is essential for perioperative risk stratification.

2.1. Essential examinations

Transthoracic echocardiography (TTE) (< 6 months) :

- Evaluation of left ventricular outflow gradient and dynamic obstruction.

- Assessment of left ventricular function and associated mitral regurgitation.

- Detection of diastolic dysfunction.

12-lead ECG :

- Identification of left ventricular hypertrophy (LVH).

- Screening for arrhythmias or conduction abnormalities.

Holter ECG (if syncope or suspected arrhythmia) :

- Monitoring for ventricular tachycardia and possible malignant arrhythmias.

Exercise stress test or stress echocardiography (if effort intolerance present) :

- Functional assessment and potential worsening of LVOT gradient.

Cardiac MRI (if diagnostic uncertainty) :

- Accurate measurement of myocardial wall thickness.

- Detection of myocardial fibrosis (late gadolinium enhancement), a sudden cardiac death risk factor.

Laboratory Tests

- Complete blood count, electrolyte panel, creatinine (standard evaluation).

- BNP/NT-proBNP if heart failure suspected.

- Coagulation profile if anticoagulation therapy is in place.

2.3. Advanced examinations (selected cases)

- Cardiac catheterization if coronary artery disease is suspected.

- Electrophysiological study if high arrhythmic risk.

3. Pre-anesthetic medication adjustments (with a cardiologist advice)

Beta-blockers (bisoprolol, atenolol, metoprolol) :

- Maintenance or adjustment to limit tachycardia and obstruction.

- Caution against abrupt withdrawal.

Verapamil or disopyramide if beta-blockers are not tolerated.

Anticoagulation management if atrial fibrillation is present.

4. Conclusion

The presence of a septal bulge necessitates a specific anesthetic strategy to minimize the risk of LVOT obstruction. A detailed cardiologic assessment, particularly with echocardiography, ECG and functional tests is essential before any GA. Heart rate stabilization, volume optimization, and careful anesthetic agent selection are key principles in its management.

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