Relative to Different Techniques Used to Relieve Right Ventricular Outflow Obstruction
Lorielyn G. Mandigma, MD; Ma. Bernadette A. Azcueta, MD; Corazon A. Estevanez, MD; Mercilyn Yap, MD
Introduction
Tetralogy of Fallot (TOF) is the most common Cyanotic Congenital Heart Disease, with an incidence of approximately 0.5/1000 live births (5% to 7% of congenital heart lesions).[1] Before the advent of surgical intervention, about 50% of patients with Tetralogy of Fallot died in the first few years of life, and it was unusual for a patient to survive more than 30 years.[2] Most patients died in childhood with a rate of survival of 66% at 1 year of age, 40% at 3 years, 11% at 20 years and 3% at 40 years.[1,2] Nowadays, with the advent of surgical repair, which includes closure of the Ventricular Septal Defect (VSD) and relief of Right Ventricular Outflow Tract (RVOT), the long-term survival of TOF patients has been greatly improved.[1]
Nevertheless, a myriad of potential complications have been reported in operated TOF patients that underlie the importance of follow-up after surgery, even if they remain asymptomatic.[1] These complications include rhythm and conduction disorders such as: sudden cardiac deaths, pulmonary regurgitation (PR) with RV dilatation and dysfunction residual RVOT obstruction. These complications may lead to subsequent hospitalizations, repeat operations, arrhythmias, and heart failure, as well as death following initial corrective surgery.[1]
These relevant postoperative residues bring about limitation in the right ventricular function and, accordingly, the quality of life and life expectancy.
Review of Related Literature
Reparative surgery for TOF should ideally result in complete closure of the VSD, preservation of right ventricular form and function, with an unobstructed right ventricular outflow tract incorporating a competent pulmonary valve.[3] Successful repair through a right ventriculotomy was first achieved by Lillehei and Varco, using “controlled cross-circulation” in 1954.[4] Kirklin et al. was the first to use a pump oxygenator for the repair of TOF 1 year later.[5] Improvements in cardiopulmonary bypass technology, as well as in surgical technique and perioperative care made early repair feasible with low morbidity and mortality.[6] Transatrial/transpulmonary repair of TOF, which was first reported in 1963 by Hudspeth et al., has been an important step in the evolution of TOF surgery.[7] It was re-introduced by Edmunds et al. in 1976, and popularized in recent years. The benefits of the transatrial/transpulmonary approach are believed to derive from eliminating a right ventriculotomy, which may lead to late right ventricular (RV) dilatation and dysfunction, as well as increased risk of ventricular ectopic activity.[8] At our center, Tetralogy of Fallot correction has been performed since 1975 when the center became operational. Since 1980, a local study by Bote-Nunez et al., has shown that both transannular patch and valve-sparing techniques are already being performed, and have had excellent late survival with only three known late deaths due to cardiac-related causes.9 Subjects included in the study belong to functional Class I and II. Residual pulmonary stenosis was also noted on 2D echocardiogram in 60% of the subjects.[9]
A study by Murphy et al. on the long-term outcome in patients undergoing surgical repair of Tetralogy of Fallot showed an overall survival rate of 95% 5 years after operation, 92% after 10 years and 15 years, 91% after 20 years, 87% after 25 years and 86% after 32 years.[10] According to age at the time of operation: 30-year survival was 90% for less than 5 years old, 93% for 5 to 7 years old, 91% for 8 to 11 years old, and 76% for more than 12-years-old.[10] According to patching of pulmonary annulus, 30-year survival was 87% for those without pulmonary outflow patch, 85% for those who had patching through the annulus, and 88% for those who had patching up to the annulus.[10]
Despite the high number of favorable outcome as shown in several studies, several potential complications have been identified and warrant the need for long-term follow-up.
In the study by Cardoso et al., restrictive RV physiology was seen on follow-up of most patients.[11] Incidence varied from 50%-70% in the study by Gatzolius et al. Restrictive physiology increases the chance of ventricular arrhythmia and sudden cardiac death.[12]
Pulmonary regurgitation (PR) complicating surgical repair of TOF is common in all patients, with over 80% having at least moderate-to-severe PR. PR has been shown to be related to the use of a transannular patch during RVOT reconstruction and aggressive infundibulectomy involving the pulmonary valve annulus. The adverse effects of PR include: progressive dilatation of RV, reduced exercise capacity, arrhythmia and sudden death.[13]
Impaired exercise capacity after complete repair of Tetralogy of Fallot is directly related to the degree of residual pulmonary regurgitation.[14]
Significance of the Study
The aim of this study was to provide current data on the surgical outcome of Tetralogy of Fallot patients who underwent repair at our institution. It also aimed to help establish a guideline on post-operative monitoring and follow-up.
To read the full article, please go to the February 2016 Issue of CCT.