The term "unseptatable" has been applied to the hearts of patients with complex systemic and pulmonary venous anatomy commonly characterized by atrioventricular canal defects and conotruncal anomalies. These patients have traditionally been treated with univentricular palliation, which leaves them subject to poor long-term survival and few rescue options if the univentricular circulation begins to fail.
The ventricular switch involves biventricular conversion (or septation) in these so-called unseptatable hearts. “We use both ventricles, with the morphologic left ventricle serving as the subpulmonary ventricle to recapitulate the physiology of congenitally corrected transposition of the great arteries.” Dr. Najm, who led the development of the novel approach, explains. “We have formalized a combination of procedures that lead to a systemic right ventricle, as opposed to a single ventricle, in patients whose hearts have multiple abnormal connections.”
All patients were alive at the last follow-up (median, 0.6 years; range, one month to 2.7 years). The left ventricular recruitment substantially improved functional status in all patients. Hypoxemia was resolved, with mean systemic oxygenation saturation improving from 79% ± 7% to 95% ± 5% (P = 0.003).
Since the report of these five cases, the Cleveland Clinic team has applied the ventricular switch to four additional patients — with some refinements, as enumerated below.
Dr. Najm notes that the ventricular switch is a series of five sequential steps outlined in the team’s published report of their initial five cases:
- Septation of the atrioventricular valves
- Repair of anomalous pulmonary venous connections
- Atrial conversion
- Rerouting of extracardiac systemic venous connections
- Left ventricle-pulmonary artery (LV-PA) conduit insertion
“This is not a single procedure but rather multiple procedures that culminate in the use of the right ventricle for systemic circulation,” he explains. “We believe these various components of the ventricular switch should be staged into two or three operations rather than all done in a single operation.” He adds that the specifics of the staged breakdown of procedures should be left to the surgeon and informed by the child’s development and overall management.
“As we gain experience, we believe the ventricular switch should be done early in life — ideally before age two years,” Dr. Najm observes. “The idea is to set these patients up with an alternative to the univentricular heart at the beginning of their lives and to undertake the ventricular switch as part of the planning for their long-term care. The heart that is prepared early in life is apt to fare better than the heart prepared later.”
He notes, however, that this is currently only a clinical impression that has not been evaluated in clinical trials. And he emphasizes that it does not mean the ventricular switch should not be considered later, as four of the five initial patients were well beyond age two and have had positive results thus far.
When the right ventricle becomes the systemic ventricle as a result of the ventricular switch, the atrioventricular valve, which is usually on the right side, may dilate and leak as a result of being pressurized. As a result, Dr. Najm’s team has begun routinely adding a left atrioventricular valve ring as a prophylactic measure to preserve the competency of the valve.
In patients requiring one-and-a-half ventricle repair — as was the case in one of the five initial patients — a pulsatile bidirectional Glenn procedure is required. The team is now adding a branch pulmonary artery band before performing the Glenn to reduce the pulsatility of the Glenn and thereby reduce the risk of postoperative pleural effusion.
The significance and innovation of this ventricular switch approach is noted by two commentaries that accompanied the publication of Cleveland Clinic’s initial case series in JTCVS Techniques. Sitaram Emani, MD, of Boston Children’s Hospital called the report “a very important contribution to the field.” David Barron, MD, of the Hospital for Sick Children in Toronto, wrote of the series: “Even when there is no immediately apparent surgical option, standing back and thinking outside the box can sometimes provide unexpected and innovative solutions.”
Both commentaries note eagerness for long-term data on patients undergoing the ventricular switch, a sentiment shared by Dr. Najm. He says his team will continue following the initial five cases and subsequent patients with a particular focus on the function of the right ventricle over time.
Another thing he’ll be watching is what potential failure of the ventricular switch’s systemic circulation may look like. “Our new approach offers patients a better quality of life through a biventricular circulation, and we’re hopeful it will offer greater survival than with univentricular circulation.” Dr. Najm says. “But we also expect it will set patients up for a better failure model if and when failure develops.”
He explains that when failure sets it with a univentricular heart after a Fontan procedure, it manifests as multiorgan failure, with high risk of liver cirrhosis, kidney failure, protein-losing enteropathy and more. “In contrast,” he says, “patients with biventricular circulation will fail with a heart failure pathophysiology, without all the multisystem components. That means they can be considered for heart transplantation or mechanical circulatory support, or other heart-specific options. These patients are set up for a more manageable failure model if needed, one with alternatives.”