Abstract
- 1.
Whenever possible, use only MRI-compatible devices in patients with CHD.
- 2.
CRT should be considered as an important therapeutic option in patients with systemic ventricular failure.
- 3.
All intracardiac shunts should be eliminated prior to placement of an endocardial device.
- 4.
In ACHD patients who do not respond to pharmacologic therapy for AF, catheter ablation of either all pulmonary veins or culprit veins should be considered.
- 5.
β blocker therapy should be considered in all ACHD patients with systemic ventricular dysfunction and NSVT.
Keywords
Cardiac resynchronization therapy, Complete heart block, Congenitally corrected transposition of the great arteries, Risk stratification, Sudden cardiac death, Systemic right ventricle
Case Details
History of Presenting Medical Complaint
A 38-year-old man presented to his local hospital with a 9-month history of expectorating small volumes of hemoptysis preceded by exertional dyspnoea for 4–5 months. He also gave a history of two brief episodes of dizziness but no syncope. He was referred following a recording of his 12 lead ECG which showed complete heart block (CHB) ( Fig. 8.1 ).
Echo demonstrated that he had congenitally corrected transposition of the great arteries (ccTGA) with a mildly dilated systemic right ventricle (RV) with severely impaired function and moderate systemic tricuspid valve (TV) regurgitation into a dilated left atrium. The subpulmonic, morphologic left ventricle (LV) was also severely impaired with trivial mitral regurgitation. There was no ventricular septal defect. There was a small atrial shunt with left to right flow.
He initially underwent implantation of dual chamber pacemaker. A transesophageal echo was performed under general anesthesia at the same time as pacemaker implantation and cardiac catheterization. This showed that there was moderate systemic right ventricular impairment, moderate-to-severe systemic tricuspid regurgitation, and severely impaired subpulmonic left ventricular function.
He was then readmitted with decompensated heart failure. This admission was preceded by 10 days of worsening shortness of breath, abdominal discomfort, and anorexia. He had hepatorenal decompensation with ALT 830 iu/L (<40) (normal values in brackets); ALP 119 iu/L (30–130); Bilirubin 53 umol/L (2–21); Urea 19 mmol/L (2.5–7.8); Creatinine 179 umol/L (64–104); and eGFR 37 mL/min/1.73 m 2 . He was diuresed and commenced on dobutamine. His clinical condition marginally improved. Symptomatically he remained in NYHA III off inotropes, but he was accepted for an assessment at our local cardiac transplant center due to our concerns of his declining status. After continued diuresis and further optimization of his medical therapy, he continued to improve, with a reduction in his pulmonary artery pressure (PAP) and was deemed too fit for cardiac transplantation.
He is now stable on medical treatment and is symptomatically NYHA class II. He has had no further admissions due to decompensated heart failure for over 12 months. His hemoptysis has entirely resolved with reduction in his pulmonary pressures. A recent cardiopulmonary exercise test (Jan 2017) using bike ergometry at 15 W ramp staging remeasured his peak VO 2 at 19.7 mL/kg/min at an respiratory exchange ratio (RER) of 1.56. He exercised for 13 min 2 s.
Admission Blood Tests (Normal Values Given in Brackets)
Hb 173 g/L (135–180); WCC 8.7 10 9 /L (4.00–11.00); Plt 197 10 9 /L (150–400)
NTproBNP levels
2013 ng/L (11/01/16)
157 ng/L (25/10/16)
Current
Hb 115 g/L (135–180);
Sodium 140 mmol/L (133–146);
Potassium 4.9 mmol/L (3.5–5.3);
Urea 10.9 mmol/L (2.5–7.8);
Creatinine 123 umol/L (64–104).
Observations
On initial presentation:
Blood pressure 147/100;
Heart rate 60 per minute;
Saturations in room air 97%.
Past Medical History and Medication (Prior to Initial Admission)
Gout—treated with allopurinol
Current Medications (2017)
Spironolactone 25 mg od
Digoxin 125 mcg od
Bumetanide 2 mg twice daily
Entresto 50 mg twice daily
Carvedilol 12.5 mg twice daily
Metformin 500 mg od
Edoxaban 30 mg od
Social History
Nonsmoker and no alcohol intake.
Father of five children.
Works as a charity worker.
Electrocardiogram
Admission 12 lead ECG showed CHB with a junctional escape rhythm at a rate of 50 per minute (see traces) ( Fig. 8.1 ).
CT Pulmonary Angiogram
Dilated pulmonary arteries. No pulmonary embolism to account for raised pulmonary artery pressure.
Cardiac Catheterization
Right PAP 62/40 mmHg; Left PAP 67/28 mmHg; Aortic pressure 63/35 mmHg.
Cardiac Catheterization—Post Diuresis at Transplant Center
Right atrial pressure 5 mmHg; PAP 43/13 mmHg; mean PAP 25 mmHg; wedge pressure 17 mmHg with V wave to 21 mmHg; cardiac index 2.2 L/min/m 2 ; pulmonary vascular resistance 2.2 Woods Units; transpulmonary gradient 8 mmHg.
Dual Chamber Pacemaker (ECG)
An endocardial dual chamber pacemaker with leads to the right atrium and the morphologic LV was implanted and set to pace in dual chamber (DDD) mode at 60–150bpm. With atrial tracking and ventricular pacing the BP was greatly improved (89–90 systolic) ( Figs. 8.2–8.4 ).
Because of the readmission with recurrent congestive heart failure he underwent upgrade to a biventricular-implantable cardiac defibrillator. (Chest X-ray Figure, EMGs and biventricular paced ECG, coronary sinus selected shots— Figs. 8.5–8.7A and B )
He now has episodes of nonsustained ventricular tachycardia (NSVT) seen on device follow-up plus episodes of atrial fibrillation (AF) so he was commenced on a direct oral anticoagulant.
Questions
- 1.
How would one risk stratify a patient with ccTGA (or perhaps a patient with a systemic RV) to mitigate against the risk of sudden cardiac death (SCD)?
- 2.
What is the role of electrophysiology (EP) studies, signal-averaged ECG, and perhaps heart rate turbulence (HRT) and also of how useful is imaging to assist in risk stratification?
- 3.
What is the role of biventricular pacing in patients with ccTGA? Should he have directly had a biventricular-implantable cardiac defibrillator without the intervening step of a dual chamber pacemaker?
- 4.
What should be done with his current tachyarrhythmias?
Consultant Opinion #1
- Oktay Tutarel, MD, FESC
- Gabriele Hessling, MD
This is an interesting case of a patient first diagnosed with ccTGA with CHB and biventricular failure at the age of 38 years.
Patients with isolated ccTGA [i.e., without associated congenital heart defects (CHDs)] may go unrecognized until the third or fourth decade of life due to lack of symptoms. Survival into the sixth or seventh decade of life has been reported. Long-term outcome is mainly defined by associated anomalies, arrhythmias, systemic atrioventricular (AV) valve regurgitation, and systemic right ventricular failure.
Interestingly, this patient presented not only with impairment of the systemic RV but also of the subpulmonic LV. This is unusual and needs further investigation. One possible cause is the development of pulmonary hypertension, which has been reported in patients with complete transposition of the great arteries (TGA) The mean PAP in this patient was 25 mmHg after treatment for heart failure. Coronary artery disease could also be a cause of ventricular dysfunction and coronary angiography might be advisable. Additionally, an MRI would also be valuable for further assessment. On a side note—as adult congenital heart disease (ACHD) patients often need an MRI for diagnostic reasons—the implementation of MRI-approved devices is recommended.
The issue of risk stratification for SCD in patients with ccTGA is challenging. While progressive failure of the systemic RV was reported as the most common cause of death in patients with ccTGA, sudden death is also encountered. Tachyarrhythmia risk, implantable cardioverter-defibrillator (ICD) implant risks, long-term outcomes, and rates of appropriate and inappropriate ICD therapies are not well studied and characterized in this patient population. While it is reasonable to implant an ICD for secondary prevention, there is no good evidence for directing our therapy to primary prevention of SCD. Furthermore, up to 20% of SCDs in CHD may be due to nonarrhythmic causes such as cerebral or pulmonary embolism and aortic or aneurysmal rupture not amenable to ICD therapy. Nonetheless, SCD in an otherwise clinically asymptomatic ccTGA patient was observed at an unexpectedly high rate in one of the largest series (1 death per 109 patient-years). In that study, the authors could not identify any clinical predictors of SCD.
We have more data in patients after atrial switch operation for complete TGA. Although these patients have other associated complications and are not an ideal comparison cohort for ccTGA patients, both cohorts have a systemic RV. In one study, sustained VT/SCD was more likely to occur in patients with associated anomalies and impaired systemic ventricular function. Patients with a QRS duration ≥140 ms were at the highest risk. In a Dutch study, symptoms of arrhythmias or heart failure at most recent follow-up and a history of documented supraventricular arrhythmias were the best predictors, whereas Holter ECG was not predictive for SCD. In a multicenter study of patients with TGA and atrial switch with an ICD, supraventricular arrhythmias seemed to be implicated in the etiology of VT, while treatment with β-blockers was protective. Inducible VT at an EP study did not predict future events. In a recent study including patients with ccTGA (n = 25) and TGA after atrial switch operation (n = 63), it was reported that right ventricular end-diastolic volume index measured by MRI or CT and peak systolic blood pressure (SBP) on exercise testing were the best predictors of adverse clinical events (including death, worsening heart failure, and arrhythmias). These predictors were similar in those with ccTGA and those with TGA and an atrial switch operation.
Rydman et al. reported that systemic right ventricular fibrosis detected by MRI was associated with clinical outcomes, mainly supraventricular arrhythmias, in TGA patients after an atrial switch operation. Therefore, imaging with late gadolinium enhancement could play a more prominent role for risk assessment in the future. While signal-averaged ECGs have been proposed as useful markers in patients after right ventriculotomy, its role in ccTGA patients is not well defined.
Current guidelines state that ICD therapy may be reasonable in adults with a systemic right ventricular ejection fraction <35%, particularly in the presence of additional risk factors such as complex ventricular arrhythmias, unexplained syncope, NYHA functional class II or III symptoms, QRS duration ≥140 ms, or severe systemic AV valve regurgitation. Technical challenges of ICD implantation may arise especially in ccTGA patients and residual intracardiac shunts or dextrocardia. These should also be accounted for when considering ICDs for primary prevention in patients with ccTGA.
Deterioration in systemic ventricular function has been reported following univentricular pacing in ccTGA patients. It was proposed that all patients with ccTGA who develop CHB should undergo primary biventricular pacing to prevent late systemic ventricular dysfunction. Current guidelines recommend that CRT can be useful for adults with a systemic right ventricular ejection fraction below 35%, at least NYHA functional class II and complete right bundle branch block with a QRS complex >150 ms (spontaneous or paced). Furthermore, CRT can be useful in adults with CHD, a systemic ventricular ejection fraction <35%, an intrinsically narrow QRS complex, and at least NYHA class II symptoms who undergo device implantation or device replacement if a requirement for a significant amount (>40%) of ventricular pacing is anticipated. Keeping in mind the anatomic variations of the coronary sinus in ccTGA patients, primary biventricular pacing may be reasonable. Nonetheless, ventricular function should be monitored closely after pacing is initiated.
Episodes of AF and of NSVT were detected on the patient’s ICD follow-up. Rhythm control is generally recommended as the initial strategy for patients with moderate or complex forms of CHD. The loss of sinus rhythm, even with a controlled heart rate, can have an important adverse impact both on hemodynamics and ventricular function in ACHD patients.
Antiarrhythmic drugs have been, for a long time, the only treatment used in CHD patients but not always with success. Koyak et al. investigated the efficacy of antiarrhythmic drugs in 92 CHD patients (68% atrial fibrillation). Class III drugs (amiodarone) were the most effective to prevent recurrences but at the same time were the drugs with the most side effects (thyroid toxicity). Specific recommendations for AF ablation in CHD population have not yet been developed due to scarcity of published data. Philip et al. reported their experience in a cohort of 36 ACHD patients, but there were no ccTGA patients in this report. In their patient population, a single pulmonary vein isolation was successful in 42% of patients at 300 days of follow-up with success rates, left atrial size, and complication rates similar in the CHD and the non-CHD group. Catheter ablation for AF might therefore be discussed with the patient, especially if his or her AF episodes are highly symptomatic.
Data about VT ablation in ccTGA patients are scarce. Corresponding to other entities of nonischemic cardiomyopathy, the substrate in nonoperated systemic RVs might be complex and variable, thereby limiting ablation success. Regarding our patient, from findings in the TGA/atrial switch population, no medical therapy other than β-blockade seems to be recommendable for the finding of NSVT.
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