Shankar Sridharan

Physiological and Clinical Consequences of Relief of Right Ventricular Outflow Tract Obstruction Late After Repair of Congenital Heart Defects

Background— Right ventricular outflow tract obstruction (RVOTO) is a common problem after repair of congenital heart disease. Percutaneous pulmonary valve implantation (PPVI) can treat this condition without consequent pulmonary regurgitation or cardiopulmonary bypass. Our aim was to investigate the clinical and physiological response to relieving RVOTO. Methods and Results— We studied 18 patients who underwent PPVI for RVOTO (72% male, median age 20 years) from a total of 93 who had this procedure for various indications. All had a right ventricular outflow tract (RVOT) gradient >50 mm Hg on echocardiography without important pulmonary regurgitation (less than mild or regurgitant fraction <10% on magnetic resonance imaging [MRI]). Cardiopulmonary exercise testing, tissue Doppler echocardiography, and MRI were performed before and within 50 days of PPVI. PPVI reduced RVOT gradient (51.4 to 21.7 mm Hg, P<0.001) and right ventricular systolic pressure (72.8 to 47.3 mm Hg, P<0.001) at catheterization. Symptoms and aerobic (25.7 to 28.9 mL · kg−1 · min−1, P=0.002) and anaerobic (14.4 to 16.2 mL · kg−1 · min−1, P=0.002) exercise capacity improved. Myocardial systolic velocity improved acutely (tricuspid 4.8 to 5.3 cm/s, P=0.05; mitral 4.7 to 5.5 cm/s, P=0.01), whereas isovolumic acceleration was unchanged. The tricuspid annular velocity was not maintained on intermediate follow-up. Right ventricular end-diastolic volume (99.9 to 89.7 mL/m2, P<0.001) fell, whereas effective stroke volume (43.7 to 48.3 mL/m2, P=0.06) and ejection fraction (48.0% to 56.8%, P=0.01) increased. Left ventricular end-diastolic volume (72.5 to 77.4 mL/m2, P=0.145), stroke volume (45.3 to 50.6 mL/m2, P=0.02), and ejection fraction (62.6% to 65.8%, P=0.03) increased. Conclusions— PPVI relieves RVOTO, which leads to an early improvement in biventricular performance. Furthermore, it reduces symptoms and improves exercise tolerance. These findings have important implications for the management of this increasingly common condition.

Assessment of differential branch pulmonary blood flow: a comparative study of phase contrast magnetic resonance imaging and radionuclide lung perfusion imaging.

Objectives: To test whether magnetic resonance (MR) imaging can be used to assess differential lung blood flow as accurately as isotope lung perfusion studies in patients investigated for congenital heart disease. Methods and results: Radionuclide lung perfusion and MR imaging were performed in 12 children with suspected unilateral branch pulmonary artery stenosis (mean age 12.1 (5.9) years, range 3.1–17.2 years). A non-breath hold, fast gradient echo phase contrast MR sequence was used to measure flow in the pulmonary trunk and one pulmonary artery to calculate differential flow. Good agreement was shown between the two imaging methods by Bland-Altman analysis. There was excellent correlation between the radionuclide and MR phase contrast calculated total lung blood flow (r  =  0.98, p < 0.0001). Conclusion: MR phase contrast is an accurate method for measuring differential total right and left lung blood flow. If MR imaging is performed to assess the branch pulmonary arteries, differential lung blood flow can be also measured, avoiding the need for an additional radionuclide lung perfusion scan and reducing the overall radiation burden to this group of patients.

Images in cardiovascular medicine. Transcatheter right ventricular outflow tract intervention: the risk to the coronary circulation.

A14-year-old male with degeneration of his right ventricular to pulmonary artery homograft conduit was referred to us for percutaneous pulmonary valve implantation (PPVI).1 Magnetic resonance imaging indicated close proximity of the left anterior descending coronary artery to the homograft (Figure, A). To test whether PPVI would compress the coronary artery, an 18-mm Mullins balloon (NuMed Inc, Hopkinton, NY) was inflated within the homograft, bringing it to its maximum diameter and mimicking stent implantation. Simultaneous selective coronary angiography demonstrated significant compression of the left anterior descending coronary artery (Figure, B). The balloon was deflated, after which normal coronary flow was restored (Figure, C), and thus PPVI was not performed. The patient was referred for surgery. Sources of Funding Dr Coats has received a British Heart Foundation Junior Fellowship Grant. Dr Taylor’s work is funded by an HEFCE grant. Dr Bonhoeffer has received a British Heart Foundation Programme Grant.A 14-year-old male with degeneration of his right ventricular to pulmonary artery homograft conduit was referred to us for percutaneous pulmonary valve implantation (PPVI).1 Magnetic resonance imaging indicated close proximity of the left anterior descending coronary artery to the homograft (Figure, A). To test whether PPVI would compress the …

Transcatheter Right Ventricular Outflow Tract Intervention The Risk to the Coronary Circulation

A14-year-old male with degeneration of his right ventricular to pulmonary artery homograft conduit was referred to us for percutaneous pulmonary valve implantation (PPVI).1 Magnetic resonance imaging indicated close proximity of the left anterior descending coronary artery to the homograft (Figure, A). To test whether PPVI would compress the coronary artery, an 18-mm Mullins balloon (NuMed Inc, Hopkinton, NY) was inflated within the homograft, bringing it to its maximum diameter and mimicking stent implantation. Simultaneous selective coronary angiography demonstrated significant compression of the left anterior descending coronary artery (Figure, B). The balloon was deflated, after which normal coronary flow was restored (Figure, C), and thus PPVI was not performed. The patient was referred for surgery. Sources of Funding Dr Coats has received a British Heart Foundation Junior Fellowship Grant. Dr Taylor’s work is funded by an HEFCE grant. Dr Bonhoeffer has received a British Heart Foundation Programme Grant.A 14-year-old male with degeneration of his right ventricular to pulmonary artery homograft conduit was referred to us for percutaneous pulmonary valve implantation (PPVI).1 Magnetic resonance imaging indicated close proximity of the left anterior descending coronary artery to the homograft (Figure, A). To test whether PPVI would compress the …

Optimizing imaging after coarctation stenting: The clinical utility of multidetector computer tomography

Following stenting for coarctation of the aorta, it can be difficult to image the stent adequately using cross‐sectional echocardiography. Unless there is marked clinical concern regarding stent patency, repeat cardiac catheterization is not warranted. Multidetector computed tomography (MDCT) is a useful alternative imaging modality. We report a case that highlights the clinical utility of MDCT for imaging patients who have had stenting of aortic coarctation. MDCT clearly revealed stent fracture as the cause of late stent failure and recoarctation.

Aberrant subclavian artery origin in tetralogy of Fallot with pulmonary stenosis is associated with chromosomal or genetic abnormality.

We determined the relationship between aortic arch anatomy in tetralogy of Fallot with pulmonary stenosis and chromosomal or genetic abnormality, by performing analysis of 257 consecutive patients undergoing surgical repair from January, 2003 to March, 2011. Chromosomal or genetic abnormality was identified in 49 of the 257 (19%) patients. These included trisomy 21 (n = 14); chromosome 22q11.2 deletion (n = 16); other chromosomal abnormalities (n = 9); CHARGE (n = 2); Pierre Robin (n = 2); and Kabuki, Alagille, Holt-Oram, Kaufman McKusick, Goldenhar, and PHACE (n = 1 each). Aortic anatomy was classified as left arch with normal branching, right arch with mirror image branching, left arch with aberrant right subclavian artery, or right arch with aberrant left subclavian artery. Associated syndromes occurred in 33 of 203 (16%) patients with left arch and normal branching (odds ratio 1); three of 36 (8%) patients with right arch and mirror image branching (odds ratio 0.4, 95% confidence interval 0.1-1.6); seven of eight (88%) patients with left arch and aberrant right subclavian artery (odds ratio 36, 95% confidence interval 4-302); and six of 10 (60%) patients with right arch and aberrant left subclavian artery (odds ratio 8, 95% confidence interval 2-26). Syndromes were present in 13 of 18 (72%) patients with either right or left aberrant subclavian artery (odds ratio 15, 95% confidence interval 4-45). Syndromes in patients with an aberrant subclavian artery included trisomy 21 (n = 4); chromosome 22q11.2 deletion (n = 5); and Holt-Oram, PHACE, CHARGE, and chromosome 18p deletion (n = 1 each). Aberrant right or left subclavian artery in tetralogy of Fallot with pulmonary stenosis is associated with an increased incidence of chromosomal or genetic abnormality, whereas right aortic arch with mirror image branching is not. The assessment of aortic arch anatomy at prenatal diagnosis can assist counselling.

Sequential segmental analysis of the crocodilian heart

Differences between hearts of crocodilians and those of mammals and birds are only partly understood because there is no standardised approach and terminology for describing cardiac structure. Whereas most reptiles have an undivided ventricle, crocodilians have a fully septated ventricle. Their hearts, therefore, are more readily comparable with the hearts of mammals and birds. Here, we describe the heart of a crocodile (Crocodylus noliticus). We use the versatile sequential segmental approach to analysis, juxtaposing several key views of the crocodilian heart to the comparable views of human hearts. In crocodiles, the atrial and ventricular septums are complete but, unlike in placental mammals, the atrial septum is without an oval fossa. The myocardial component of the crocodilian ventricular septum dominates, but the membranous septum likely makes up a greater proportion than in any mammal. In the crocodile, the aortic trunk takes its origin from the left ventricle and is not wedged between the atrioventricular junctions. Consequently, there is a common atrioventricular junction, albeit with separate right and left atrioventricular valvar orifices. As in mammals, nonetheless, the crocodilian left atrioventricular valvar orifice is cranial to the right atrioventricular valvar orifice. By applying a method of analysis and terminology usually restricted to the human heart, we build from the considerable existing literature to show neglected and overlooked shared features, such as the offset between the left and right atrioventricular valvar orifices. Such commonalities are surprising given the substantial evolutionary divergence of the archosaur and synapsid lineages, and likely reflect evolutionarily shared morphogenetic programmes.

Late donor cardiectomy after paediatric heterotopic cardiac transplantation

BACKGROUND Cardiac transplantation is a life-saving procedure in infants and children with advanced cardiomyopathy. However, it is greatly limited by shortage of paediatric donors and the complications of long-term immunosuppression, including post-transplant lymphoproliferative disorder (PTLD). We report the management of an infant who had heterotopic cardiac transplantation for advanced cardiomyopathy with secondary pulmonary hypertension who developed seemingly incurable PTLD. METHODS An 8-month-old girl presented in 1994 with signs of severe heart failure, secondary to dilated cardiomyopathy. At age 11 months, the patient underwent a heterotopic cardiac transplantation. FINDINGS The patient developed many episodes of PTLD associated with Epstein-Barr virus infection that were resistant to several therapies, including reduction of immunosuppression. Native heart recovery enabled removal of the donor heart 10.5 years after the original operation to allow complete cessation of immunosuppression. Her postoperative course was uncomplicated and the outcome was excellent. 3.5 years after surgery, the patient remains well, in complete remission from her PTLD, and has normal cardiac function. INTERPRETATION This case shows several issues relating to the use of heterotopic cardiac transplantation in infants and the capacity of the heart to recover. It also provides new insights into the interaction between the immune system with several aspects of modern management of post-transplantation PTLD. FUNDING None.

Flecainide versus digoxin for fetal supraventricular tachycardia: Comparison of two drug treatment protocols

BACKGROUND The optimal treatment for fetal supraventricular tachycardia (SVT) with 1:1 atrioventricular relationship is unclear. OBJECTIVE We compared the effectiveness of transplacental treatment protocols used in 2 centers. METHODS Pharmacologic treatment was used in 84 fetuses. Maternal oral flecainide was the primary therapy in center 1 (n = 34) and intravenous maternal digoxin in center 2 (n = 50). SVT mechanism was classified by mechanical ventriculoatrial (VA) time intervals as short VA or long VA. Treatment success was defined as conversion to sinus rhythm (SR), or rate control, defined as >15% rate reduction. RESULTS Short VA interval occurred in 67 fetuses (80%) and long VA in 17 (20%). Hydrops was present 28 of 84 (33%). For short VA SVT, conversion to SR was 29 of 42 (69%) for digoxin and 24 of 25 (96%) for flecainide (P = .01). For long VA SVT, conversion to SR and rate control was 4 of 8 (50%) and 0 of 8, respectively, for digoxin, and 6 of 9 (67%) and 2 of 9 (cumulative 89%) for flecainide (P = .13). In nonhydropic fetuses, digoxin was successful in 23 of 29 (79%) and flecainide in 26 of 27 (96%) (P = .10). In hydrops, digoxin was successful in 8 of 21 (38%), flecainide alone in 6 of 7 (86%, P = .07 vs digoxin), and flecainide ± amiodarone in 7 of 7 (100%) (P = .01). Intrauterine or neonatal death occurred in 9 of 21 hydropic fetuses treated with digoxin (43%), compared to 0 of 7 (P = .06) treated with flecainide. CONCLUSIONS Flecainide was more effective than digoxin, especially when hydrops was present. No adverse fetal outcomes were attributed to flecainide.

Timing of removal of pacing wires following paediatric cardiac surgery

BACKGROUND Temporary percutaneous epicardial pacing wires are routinely placed in children following cardiac surgery. There is uncertainty in clinical practice about the optimum timing for their removal, and practice varies widely both within and between different institutions. AIM The aim of our study was to describe the use of temporary pacing in children undergoing cardiac surgery. METHODS We performed a prospective audit of 140 children following cardiac surgery in two institutions. Information on diagnosis, surgical procedure, occurrence of arrhythmias, use of pacing wires, timing of removal of the wire, and complications related to removal was recorded on a daily basis from clinical records. RESULTS We studied 140 patients undergoing a total of 141 operations. Of these, 39 (28%) required pacing postoperatively. In 38, pacing was required within the first 24 hours. One patient, who was in nodal rhythm for the first 24 hours, required pacing on the second postoperative day, while 29 patients required pacing beyond the first 24 hours. No patient in sinus rhythm on the first postoperative day required new pacing after this time. The median time to removal of the pacing wires was 4.5 days, with an inter-quartile range from 2 to 9 days. Complications included malfunction of atrial wires in 2 patients. CONCLUSIONS Our study shows that no patient who was in sinus rhythm for the first 24 hours post-operatively required pacing before their discharge from hospital. This suggests that, in those patients in a stable state of sinus rhythm, and who have not required pacing within the first 24 hours, it may be safe to remove pacing wires after 24 hours. This could be timed to coincide with the removal of chest drains, thus avoiding the need for multiple distressing procedures.