L-TGA & Double Inlet LV post-Fontan complicated by VF

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CardioNerds (Amit Goyal & Daniel Ambinder) join Stanford cardiology fellows (Pablo Sanchez, Natalie Tapaskar, Jimmy Tooley) for tacos while enjoying the sunshine on the Stanford Oval! They recount the story of a man with adult congenital heart disease (ACHD): L-TGA (levo-transposed great arteries) with double inlet LV post-Fontan complicated by VF arrest. Dr. Christiane Haeffele provides the E-CPR and program director Dr. Joshua Knowles provides a message for applicants. Episode notes were developed by Johns Hopkins internal medicine resident Evelyn Song with mentorship from University of Maryland cardiology fellow Karan Desai and Cleveland clinic cardiology fellow Josh Saef.

Jump to: Patient summary – Case media – Case teaching – References

The CardioNerds Cardiology Case Reports series shines light on the hidden curriculum of medical storytelling. We learn together while discussing fascinating cases in this fun, engaging, and educational format. Each episode ends with an “Expert CardioNerd Perspectives & Review” (E-CPR) for a nuanced teaching from a content expert. We truly believe that hearing about a patient is the singular theme that unifies everyone at every level, from the student to the professor emeritus.

We are teaming up with the ACC FIT Section to use the #CNCR episodes to showcase CV education across the country in the era of virtual recruitment. As part of the recruitment series, each episode features fellows from a given program discussing and teaching about an interesting case as well as sharing what makes their hearts flutter about their fellowship training. The case discussion is followed by both an E-CPR segment and a message from the program director.

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Patient Summary

A man in his mid-30s with past medical history notable for L-TGA (levo-transposed great arteries) with double inlet LV s/p Fontan palliation was playing golf when he suddenly collapsed.  EMS arrived after three minutes of bystander CPR. An AED indicated the patient had suffered a VF arrest. ROSC was achieved after 1 round of Epi and 1 shock delivered. He was intubated and started on targeted temperature management protocol. Home medications were notable for digoxin 0.25mg daily, sotalol 120mg BID, and warfarin 5mg daily. Initial labs were notable for Na 127, K 5.4, Cr 1.0 (unknown baseline), INR 4.5, Lactate 4.6, Troponin-I 0.532, VBG 7.06/61, and random Digoxin level 2.7.  EKG showed AV sequential pacing at a rate of 70 bpm. QTc prolonged at 571ms. No ischemic ST changes. Device interrogation showed sustained VT for 5 minutes prior to external shock. No internal shock was delivered. He was initially stabilized and his acidosis and hyperkalemia were corrected. Course was complicated by hemoptysis due to alveolar hemorrhagic and he was given concentrated prothrombin complex to reverse his coagulopathy. He eventually stabilized, and a formal TTE was obtained which showed a hypoplastic RV, single dilated LV with an akinetic posterior wall and hypokinetic lateral wall, all similar to his prior TTE in 2019. No obstruction noted at the IVC/Fontan anastomotic site. Coronary angiogram performed after his kidney function improved also did not show any significant obstructions or coronary anomalies. After multidisciplinary discussion, his VF arrest was attributed to a combination of prior ventricular fibrosis/scar, suspected digoxin toxicity, sotalol, dehydration, and renal failure. He had a subcutaneous ICD lead placed and was ultimately discharged home.

Case Media

A. CXR
B. ECG

Episode Schematics & Teaching

The CardioNerds 5! – 5 major takeaways from the #CNCR case

What’s Transposition of the Great Arteries (TGA)?
- TGA is defined by a nontraditional ventricle-arterial relationship so that the aorta arises from the morphological RV and the pulmonary artery (PA) arises from the morphological LV
- There are two types of TGA, L or levo and D or dextro.
  - D (rightward)-TGA: Systemic venous return flows into RA -> RV -> delivered to systemic circulation via Aorta, bypassing the lungs. The pulmonary veins flow into the LA -> LV-> delivered to the pulmonary circulation via the PA. The result is two parallel systems that fail to deliver oxygenated blood to the systemic circulation. This is not compatible with life unless another defect such as ASD, VSD, or PDA is present (or created) to allow mixing of deoxygenated and oxygenated blood. Patients with D-TGA usually require arterial switch procedures within 1 month of life. A simplified way to understand this is to say that the great vessels are malpositioned, leaving patients with two parallel circulation.
  - L (leftward)-TGA: Deoxygenated blood flows into RA -> morphologic LV in the traditional RV position -> PA -> Lungs->  LA -> morphologic RV in the traditional LV position -> aorta to deliver oxygenated blood to the body. A simplified way to understand this is to say that the ventricles are malpositioned, leaving patients with two circulations in series (normal) with the pumps in the wrong places. There’s no cyanosis at birth and patients may be completely asymptomatic for years. This is more rare than D-TGA and only occurs in ~7 per 100,000 births. 
    - The problem in L-TGA is that the morphologic RV, being the systemic ventricle, is not meant to withstand systemic afterload and can result in significant TR and ventricular dysfunction. Additionally, the majority of the cases (80%) are associated with an additional heart defect, such as VSD, pulmonary stenosis, RV hypoplasia, or DILV as in our case.  
What’s Double Inlet Left Ventricle (DILV)?
- In DILV, both atrio-ventricular valves (mitral and tricuspid) lead into the LV and a large VSD is present to connect the LV and RV. DILV is very rare (~5 in 100,000 births). It coexists with L-TGA in about 65% of the cases.
- DILV leads to mixing of oxygenated and deoxygenated blood in the LV, resulting in inadequately oxygenated blood entering the systemic circulation and also over-circulation to the pulmonary system (increased Qp:Qs), resulting in LV congestion and heart failure over time.  
What’s the Fontan procedure?
- The Fontan procedure is typically performed as a palliation procedure to direct flow of systemic venous return to the lungs without passing through a subpulmonic ventricle. It’s typically performed in patients with complex congenital heart disease with a single functioning ventricle such as tricuspid atresia, pulmonary atresia, hypoplastic left heart syndrome, and DILV. In these conditions, intracardiac mixing of oxygenated and deoxygenated blood leads to cyanosis and ventricular volume overload without surgical intervention.
- The early variation of the Fontan procedure connected the pulmonary arteries to the RA. However, this led to RA dilation and loss of contractility, resulting in decreased pulmonary blood flow and increased risk for thrombus formation and arrhythmias. More modern Fontan palliation procedures connect both vena cavae directly to pulmonary arteries (via an intra- or extra-cardiac conduit), bypassing the RA and RV completely.
- Elevated pulmonary pressure is an absolute contraindication for the Fontan procedure since there’s no ventricular contraction to pump blood through the lungs (it relies on passive flow). Therefore, the cavopulmonary Fontan circulation can’t be created at birth given the normal high pulmonary vascular resistance in newborns. 
- The modern Fontan palliation sequence is performed in a staged fashion to allow the patient’s body to adapt to the different hemodynamic states and reduce overall surgical morbidity and mortality.
  1. Stage 1: systemic-pulmonary shunt; performed during neonatal period
  - An artificial shunt is placed between a major systemic central vessel, usually subclavian artery, and proximal pulmonary artery. The goal of this step is to provide dedicated pulmonary blood flow to allow adequate oxygen delivery to tissues and pulmonary arterial growth. 
  1. Stage 2: superior cavopulmonary connection (Glenn procedure); performed between 4-12 months
  - Anastomosis is made between the SVC and proximal right PA. The previous systemic-pulmonary shunt is usually ligated. This allows priming of the pulmonary vasculature over time before completion of the Fontan circulation. 
  1. Stage 3: completion of the Fontan circulation; performed between ages 1-5.
  - Different surgical techniques are used, but the common endpoint is  IVC anastomosis to the right PA.
- After the Fontan procedure, cardiac output is completely dependent on passive flow into the lungs. LV preload is central to Fontan physiology.  Dehydration, an increase in pulmonary vascular resistance and/or worsening LV stiffness (and hence LV filling) can lead to decreased cardiac output.  
What are some complications associated with the Fontan procedure?
- RA dilatation was very common with the classic Fontan where atriopulmonary instead of cavopulmonary Fontan circulation was created, the RA is exposed to elevated pressure, leading to RA dilatation, thrombus formation, and arrhythmias.
- Ventricular failure usually develops after the first decade following completetion of the Fontan palliation. Patients will typically develop the classic symptoms of heart failure due to either HFrEF or HFpEF. Potential contributors to CHF include atrial tachycardia, valvular regurgitation, and volume-loading shunts.
- Atrioventricular valve (AVV) regurgitation can develop insidiously after the Fontan procedure and is a significant risk factor for long-term mortality post Fontan. AVV regurgitation can lead to volume overload, ventricular dilation, reduced ventricular contractility, and increased postcapillary and central venous pressures, compromising the Fontan circulation. Medical management of patients with AVV regurgitation post Fontan include diuretic therapy and afterload reduction.
- Protein-losing enteropathy (PLE) is the abnormal loss of serum proteins into the intestinal lumen and occurs in 5-12% of patients after a Fontan palliation. Its pathophysiology is incompletely understood, but thought to be due to chronic venous congestion-induced lymphatic insufficiency. PLE may lead to edema/ascites, growth failure, coagulopathy, decreased bone density, and lymphopenia.
- Plastic Bronchitis (PB) occurs in <5% of patients with Fontan and is characterized by production of thick, tenacious casts within the airway lumen. Similar to PLE, it’s believed to be due to spillage of protein-rich lymph through lymphatic-to-bronchial communications. Medical management includes diuretics, ARBs, and pulmonary vasodilators.
- Fontan associated liver disease (FALD) is a common complication after Fontan due to increased venous pressure, lymphatic overflow, and hepatic congestion. FALD spans the spectrum from liver fibrosis to cardiac cirrhosis and hepatocellular carcinoma. All patients with Fontan circulation should be counseled on avoiding hepatotoxins and undergo regular hepatic screening.  
What are the common long-term complications of congenital heart disease (CHD)?
- With advances in cardiology and cardiac surgery, 85% of neonates with CHD survive into adult life. The four most common complications seen in ACHD include Heart failure, Endocarditis, Arrhythmias, and Pulmonary Hypertension, or H.E.A.P
- Heart failure is a major cause of morbidity and mortality in ACHD patients. The pathophysiology of HF in ACHD is multifactorial and includes chronic pressure/volume ventricular loading, persistent arrhythmias, longstanding cyanosis, myocardial fibrosis, or pulmonary vascular disease. Medical management typically includes diuretics and ARBs; however, guidelines for treatment of HF in ACHD patients are lacking because all the trials excluded ACHD patients. Ultimately heart transplantation should be considered in those with refractory HF. Given high prevalence of pulmonary hypertension and RV dysfunction, the use of VADs is limited in this population.
- Endocarditis is more prevalent in patients with ACHD compared to the general population. The increased risk of IE in this population is related to both the underlying congenital defect and previous surgical interventions with reconstructed anatomy. The most common site for IE is the LV outflow tract, regardless of previous surgery. IE should be suspected in all ACHD patients presenting with fever, night sweats, or new manifestation of HF. Patients with cyanotic heart disease, history of IE, prosthetic valve, or prosthetic material/devices should receive prophylactic antibiotics prior to any invasive dental procedures.
- Arrhythmias account for the majority of ED visits in ACHD patients. For patients older than 20 years, >50% will have atrial tachyarrhythmias. Other common arrhythmias include AV node disease, PVCs, and NSVTs. Sustained ventricular arrhythmias, typically due to prior ventriculostomy scars or ventricular fibrosis, is the most common cause of SCD in the ACHD population. Additionally, pacemaker implantation in ACHD patients requires thorough understanding of underlying anatomy. At times, epicardial pacing is needed (i.e. Fontan patients) due to inability to access cardiac chambers. Pulmonary hypertension (PH) is defined as mean PAP >/= 25 mmHg, similar as in the general population. About 5-10% of ACHD patients have PH and these patients are at a higher risk for hospitalization and death. The clinical classification of ACHD-related PH has four main clinical groups: Eisenmenger’s syndrome, PAH associated with systemic-to-pulmonary shunts, PAH with small defects, and PAH after corrective cardiac surgery.