Hypertrophic Cardiomyopathy: The Role for Septal Myectomy
Hypertrophic cardiomyopathy (HCM) is one of the most common inherited heart diseases, affecting 1 out of 200 to 500 individuals in the United States. While HCM is the number one cause of sudden cardiac death in young, healthy people, many patients do not experience symptoms that affect their quality of life or serious cardiac events and consequently do not require invasive interventions. However, some 80 percent of patients experience mechanical obstruction to the left ventricular outflow (LVOT) resulting in cardiovascular complications and symptoms, including heart failure, syncope, and angina.
“In patients with HCM whose symptoms do not respond to maximal medical therapy, septal reduction therapy is performed to reduce LVOT obstruction,” says Hiroo Takayama, MD, PhD, Director, Cardiovascular Institute, and Co-Director, Hypertrophic Cardiomyopathy Center, Division of Cardiac, Vascular and Thoracic Surgery at NewYork-Presbyterian/Columbia University Irving Medical Center. Dr. Takayama is internationally recognized for performing complex aortic and hybrid aortic surgery, myectomy for obstructive hypertrophic cardiomyopathy, and heart failure surgery.
Septal Myectomy: Looks Easy, Does Hard
In a septal myectomy, the surgeon removes a small amount of the thickened septal wall to widen the outflow tract from the left ventricle to the aorta, thus eliminating the obstruction and the mitral valve regurgitation that occurs with this condition. Achieving an appropriate length and width of resection of the hypertrophic interventricular septum is technically demanding and requires substantial surgical expertise and experience.
“Conceptually, it is a simple operation,” says Dr. Takayama. “You remove the muscle that is obstructing the LVOT, but taking the right amount of muscle and creating the new heart with an appropriate shape is not easy. You must determine how much of a muscle resection is sufficient. If you remove too much, you can create a hole in the heart or injure the conduction system. If you remove too little muscle, the surgery is not successful.”
As Dr. Takayama explains, operating through the aortic valve also poses challenges. “We remove the exit muscle of the left ventricle by looking at the left ventricular muscle through the small window of the aortic valve. That restrains the surgical visualization significantly. So, for several reasons this is not an easy operation to perform.”
To overcome this hurdle, in 2019 Dr. Takayama in collaboration with his Columbia and Weill Cornell Medicine colleagues at NewYork-Presbyterian Hospital developed a virtual myectomy technique using 3D reconstruction of gated cardiac computed tomography to assist the intraoperative assessment of the adequacy of the resection. “The 3D EKG gated CT scans gave us a new understanding of the anatomy of patients with hypertrophic cardiomyopathy, revealing a ‘septal band,’ a novel discovery and a common anatomical feature of these patients,” he says.
The thickened septum, visualized as a broad-based band in 3D-printed hearts, begins underneath the left coronary annulus, runs anteriorly and obliquely in a clockwise fashion from base to apex along the septal wall, and reaches to the base of the posteromedial papillary muscles and mid inferior wall. With this information, the team developed a technique to resect the septal band in three steps.
“Through the 3D printing of several hearts in a number of patients, we determined a universal pattern of muscle hypertrophy that contributes to the obstruction of the heart,” continues Dr. Takayama. “With this EKG gated CT angiogram, we conduct the surgical planning and use a volumetric scanner of the septal band to calculate and predetermine how many pieces of the muscle we should remove. We believe this is quite innovative.”
Does SRT Prevent Acute Cardiac Events?
While septal reduction therapy has been performed for decades, it is largely unknown whether this procedure prevents HCM-related cardiovascular events or death. To this end, Dr. Takayama and colleagues at NewYork-Presbyterian/Columbia examined this issue calling on databases that capture all hospitalizations and outpatient visits in New York State. Patients identified included 752 individuals with HCM who underwent SRT between 2007 and 2014 and 5,855 controls with HCM who had never had SRT but had at least one hospitalization for HCM during the same period. The primary outcome was a composite of acute cardiovascular events and all-cause mortality during 0 to 180 days and 181 to 360 days.
The study, which was published in the September 30, 2021 issue of the International Heart Journal, was the “first to investigate the effects of SRT on acute cardiovascular manifestations and all-cause mortality compared to non-invasive management in patients with HCM.” The findings revealed that patients undergoing septal reduction therapy had a reduced risk of acute cardiovascular events and mortality in the first year following surgery.
“Septal myectomy is not a procedure that is performed by all cardiac surgeons,” says Dr. Takayama, who performs some 30 of these operations a year. “There are multiple studies indicating that the surgical outcome is driven by the surgeons or the institutional volume. Our program has one of the largest volumes in the country for myectomies. Importantly, it’s not only about the surgeon. Septal myectomy is only part of the care of patients with hypertrophic cardiomyopathy.”
NewYork-Presbyterian/Columbia’s Hypertrophic Cardiomyopathy Center, co-led by Dr. Takayama and Shepard Weiner, MD, Medical Director, comprises a team of multiple specialists in cardiology, interventional cardiology, cardiothoracic imaging, and clinical genetics who together maximize the care of patients with HCM, including access to clinical trials and cutting edge medications.
Effects of Septal Reduction Therapy on Acute Cardiovascular Events and All-Cause Mortality in Patients with Hypertrophic Cardiomyopathy. Morita SX, Zhao Y, Hasegawa K, Fifer MA, Maurer MS, Reilly MP, Takayama H, Shimada YJ. International Heart Journal. 2021 Sep 30;62(5):1035-1041.
Virtual septal myectomy for preoperative planning in hypertrophic cardiomyopathy. Takayama H, Yu SN, Sorabella R, Leb J, Pulerwitz TC, Cooper C, Argenio M, Shimada YJ, Weiner S, Ginns JN. Journal of Thoracic and Cardiovascular Surgery. 2019 Aug;158(2):455-463.