From the Guidelines
In patients with hypertrophic obstructive cardiomyopathy (HOCM) and low blood pressure, phenylephrine is generally the inotrope of choice. Phenylephrine, a pure alpha-1 adrenergic agonist, increases systemic vascular resistance and blood pressure without causing significant increases in heart rate or contractility. The typical starting dose is 100-180 mcg/min IV, titrated to effect, as suggested by the management considerations for patients with HCM 1. This medication is preferred because it avoids the beta-adrenergic stimulation that would worsen left ventricular outflow tract (LVOT) obstruction in HOCM.
Other commonly used inotropes like dobutamine, epinephrine, and norepinephrine should be avoided as they can increase contractility and heart rate, potentially worsening the dynamic LVOT obstruction characteristic of HOCM. Additionally, volume resuscitation may be beneficial in these patients if they are hypovolemic, as maintaining adequate preload helps reduce outflow obstruction, emphasizing the importance of avoiding hypovolemia and reduced preload 1. If phenylephrine is unavailable or ineffective, vasopressin might be considered as an alternative since it also lacks significant inotropic effects. The management goal is to increase afterload and blood pressure while avoiding increased contractility, which would exacerbate the pathophysiology of HOCM. It's also crucial to prioritize intravenous fluid administration to correct hypovolemia and consider intraoperative echocardiography to evaluate LVOT obstruction in the setting of hypotension, as outlined in the guidelines for perioperative cardiovascular management 1.
Key considerations in managing HOCM with low blood pressure include:
- Avoiding hypovolemia and reduced preload to prevent worsening LVOT obstruction
- Avoiding hypotension and reduced afterload
- Avoiding tachycardia to ensure adequate LV filling
- Using alpha-agonists like phenylephrine or vasopressin instead of beta-agonists
- Considering intraoperative echocardiography for evaluating LVOT obstruction in hypotension
- Maintaining sinus rhythm due to the prevalence of LV hypertrophy and decreased LV compliance in HOCM, as suggested by the guidelines 1.
From the Research
Inotrope of Choice in HOCM with Low BP
- The ideal inotrope for patients with Hypertrophic Obstructive Cardiomyopathy (HOCM) and low blood pressure is not explicitly stated in the provided studies 2, 3, 4, 5, 6.
- However, it is mentioned that cardiogenic shock due to HOCM crisis presents a clinical challenge as pharmacologic vasopressor and/or inotropic support can compromise hemodynamics and acute afterload reduction worsens left ventricular outflow tract (LVOT) obstruction 4.
- A systematic review suggests that epinephrine therapy may be detrimental to patients with HCM with hypotension or cardiac arrest, as it can increase left ventricular outflow tract obstruction 6.
- Transvenous pacing guided by bedside echocardiography has been used to restore hemodynamic stability in a patient with HOCM and low blood pressure 4.
- The choice of inotrope or other treatment modalities should be individualized based on functional status, comorbidities, local expertise, and patient preference 3, 5.
Treatment Considerations
- Septal reduction therapy, either surgical septal myectomy or alcohol septal ablation, can be effective in relieving obstruction and improving symptoms in patients with HOCM 2, 3, 5.
- Other treatment options, such as dual-chamber pacing and radiofrequency catheter ablation, may also be considered 5.
- The suitability of epinephrine in HOCM-associated cardiac arrest is questionable, and other drugs may be considered in these cases 6.