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Use of Hemodynamic Ramp Study to Optimize Continuous-Flow Ventricular Assist Device in a Fontan Patient

Chau, Peter; Lim, Heang M.; Schumacher, Kurt R.; Grifka, Ronald G.; Peng, David M.

doi: 10.1097/MAT.0000000000000920
Case Reports
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The utility of hemodynamic ramp studies in single ventricle patients supported by continuous flow left ventricular assist devices (CF-LVADs) is largely unknown. We report the novel use of the hemodynamic ramp test to optimize a 26 year-old Fontan-palliated single-ventricle patient supported with a continuous-flow ventricular assist device (Heartware HVAD). Modest improvements in Fontan hemodynamics resulted in significant and persistent clinical improvement and symptomatic relief.

From the Division of Pediatric Cardiology, CS Mott Children’s Hospital, University of Michigan, Ann Arbor, Michigan.

Submitted for consideration June 2018; accepted for publication in revised form October 2018.

Disclosure: The authors have no conflict of interest to report.

Correspondence: Peter Chau, CS Mott Children’s Hospital, 1540 East Hospital Drive, Ann Arbor, Michigan 48104. Email: pchau@med.umich.edu.

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Case Report

A 26 year old (1.86 m2 body surface area [BSA]) single ventricle patient with tricuspid atresia status-post staged repair, including a nonfenestrated lateral tunnel Fontan operation, developed postpartum cardiomyopathy with New York Heart Association (NYHA) class III symptoms attributed to severe Fontan failure with cyanosis, fatigue, and shortness of breath with minimal exertion. Echocardiograms displayed severely depressed left ventricular systolic function and severe mitral regurgitation. Cardiac catheterizations revealed elevated Fontan pressures in the low 20s and numerous systemic vein-to-pulmonary vein (V-V) and aortopulmonary collateral vessels. Several V-V collateral vessels were coil occluded with only transient improvement in systemic oxygen saturation. Oral heart failure therapies were initiated and up-titrated. Despite these interventions, the patient’s symptoms progressed over the next several months with increasing shortness of breath, fatigue, palpitations, and chest pain. She was initially evaluated for cardiac transplant at another institution; however, she was not accepted because of the complex congenital heart disease, comorbidities, and elevated panel reactive antibody (PRA) level. She was referred to our for a second opinion.

After evaluation at our institution, the decision was made to implant a Heartware ventricular assist device (HVAD), a continuous-flow left ventricular assist device (CF-LVAD), for decompensated heart failure and as bridge to transplant candidacy. In Fontan patients, undergoing primary transplant without a VAD would be clearly preferred to avoid an additional operation, sensitization, and other adverse events if possible. However, given this patient’s tenuous clinical status and long anticipated wait time because of allosensitization, we concluded that mechanical circulatory support provided the best chance to reach transplantation and for long-term survival. Since the patient had a recent diagnostic cardiac catheterization at another institution, a pre-VAD implant cardiac catheterization was not repeated. If she was well supported after recovery, she would undergo desensitization and proceed with listing for transplantation. Heartware ventricular assist device implantation and her postoperative course were uneventful and was discharged after 2 weeks. However, she remained symptomatic endorsing daily symptoms of fatigue, chest pain, and dizziness. In 6 months, she required eight admissions or emergency room evaluations for fluid overload, recurrent drive-line infections, intermittent supraventricular tachycardia, and hemoptysis secondary to esophageal varices. Because of persistent and severe “right heart” failure symptoms, in an attempt to optimize HVAD support, a combined invasive hemodynamic and echocardiographic ramp test was performed in the cardiac catheterization lab. We applied a standardized hemodynamic ramp protocol using the Ramp Test Protocol.1,2 Preoptimization, her HVAD was set at 2,500 revolutions per minute (RPM). We assessed serially the patient’s hemodynamic responses starting at 2,500 RPM and increasing by 100 RPM every 2 minutes, to a maximum of 3,200 RPM (manufacturer’s recommended upper limit). Hemodynamic parameters measured included heart rate (HR), mean Fontan pressure, left ventricular end diastolic pressure (LVEDP), arterial blood pressure (ABP), arterial oxygen saturation, and pulmonary artery saturation (i.e., Fontan or mixed venous saturation). An echocardiogram was obtained at baseline, then at regular intervals during the ramp study.

The baseline HVAD device-calculated flow was 6.8 L/min (cardiac index 3.7 L/min/m2) at 2,500 RPM, a Fontan (central venous) mean pressure of 21 mm Hg and LVEDP of 18 mm Hg. Maximal improvement in her hemodynamic parameters was observed at 3,100 RPM (Table 1, Figure 1) with a decrease in Fontan mean pressure to 18 mm Hg, LVEDP to 13 mm Hg, and a device-calculated flow of 8.5 L/min (cardiac index 4.6 L/min/m2). There were no further improvements in her hemodynamics at 3,200 RPM. By echocardiogram, there was an improvement in left ventricular diastolic dimension (LVEDD) with an LVEDD of 7.99 cm (z score + 7.6) and 7.30 cm (z score + 6.5) at 2,500 to 3,100 RPM, respectively (Table 2). Mitral regurgitation was unchanged with only trivial aortic insufficiency. Therefore, the final device setting was changed from 2,500 to 3,100 RPM. The procedure was well tolerated and without complication.

Table 1

Table 1

Table 2

Table 2

Figure 1

Figure 1

Two months after VAD optimization, she reported significant and lasting clinical improvement with NYHA class I–II symptoms (Table 3). She denied chest pain, palpitations, and shortness of breath both at rest and with exercise. She went bowling frequently and ran daily on a treadmill. She had minimal edema and significantly less diuretic requirement. She had only one nonelective admission in the 6 months following the hemodynamic ramp test and endorsed a subjectively good quality of life. Given the alternative of continued unsuccessful attempts at desensitization and a very high-risk transplant course, she elected to transition to HVAD as destination therapy.

Table 3

Table 3

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Discussion

There is a paucity of published reports on congenital heart disease (CHD) and single ventricle patients supported by CF-LVADs.3,4 As such, there is no guidance for VAD optimization in these complex patients and significant practice variability. Current guidelines on the management of patients supported on CF-LVADs may not necessarily apply to single ventricle patients.5

This case highlights several aspects and potential benefit of VAD optimization with hemodynamic ramp testing in a single ventricle Fontan patient supported by CF-LVADs. A subtle decrease in the Fontan pressure and increase in the cardiac index (calculated by Fick equation) through VAD optimization resulted in significant clinical improvement for our patient. In non-CHD heart failure patients, a significant proportion of patients have underappreciated, suboptimal hemodynamic profiles which may improve with ramp testing.1,6 Additionally, because current devices and guidelines are not designed for single ventricle patients, hemodynamic ramp testing can provide a way to better optimize device settings in this unique population.

Also, this case underscores the need for potentially higher than expected device RPMs and device flows in single ventricle patients after Fontan palliation. The patient required 3,100 RPMs which is near the manufacturer’s upper limit of 3,200 RPM, though she was relatively small (BSA of 1.86 m2). Increasing the RPM resulted in a significant increase in overall HVAD flow while the cardiac index or systemic blood flow (by the Fick method with an assumed oxygen consumption) increased minimally. This phenomenon was most likely secondary to the patient’s substantial aortopulmonary collateral blood flow in addition to the systemic blood flow. The additional aortopulmonary collateral volume load necessitates a higher overall cardiac output which is not accounted for in the Fick estimation. Furthermore, in Fontan patients, there can be significant diastolic dysfunction of the single ventricle and elevated pulmonary vascular resistance without a subpulmonary ventricle. We believe the combination of these factors, as in our patient, often requires higher than expected VAD settings in the failing Fontan circulation.

In hindsight, better preoperative characterization of collateral flow (through catheterization or magnetic resonance [MR] angiography) would have been helpful in post-VAD implant management. Although it was not performed in our case, coil occlusion of aortopulmonary collaterals (to decrease the volume load) and of V-V collaterals (to improve cyanosis) should be considered in Fontan patients requiring VAD support.

Depending on the specific mechanism of Fontan failure, alternative surgical options should be considered such as Fontan conversion/revision and valve repair. Conversion from atriopulmonary to total extracardiac cavopulmonary connection has been shown to improve symptoms and control dysrhythmia.7 In our case, both of these options were considered, but ultimately not performed as the risk of a Fontan conversion and mitral valve repair was deemed too high given her severely depressed systolic function. Furthermore, although it was not performed before VAD implantation, a cardiac MR imaging may be beneficial in determining “ideal” device-calculated flow by estimating the degree of collateral flow.

In summary, invasive ramp testing in this single ventricle Fontan patient supported by a CF-LVAD was safe and effective. With modest changes in hemodynamics, she had significant and lasting symptomatic improvement. Further experience and refinement of the postimplantation management in CHD and Fontan-palliated single ventricular patients supported by CF-LVADs are necessary to improve outcomes in this challenging group of patients.

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Reference

1. Uriel N, Sayer G, Addetia K, et al. Hemodynamic ramp tests in patients with left ventricular assist devices. JACC Heart Fail 2016.4: 208–217.
2. Uriel N, Morrison KA, Garan AR, et al. Development of a novel echocardiography ramp test for speed optimization and diagnosis of device thrombosis in continuous-flow left ventricular assist devices: The Columbia ramp study. J Am Coll Cardiol 2012.60: 1764–1775.
3. Buratto E, Shi WY, Ye XT, Konstantinov IE. Ventricular assist devices for the failing univentricular circulation. Expert Rev Med Devices 2017.14: 449–459.
4. Slaughter MS, Rogers JG, Milano CA, et al; HeartMate II Investigators: Advanced heart failure treated with continuous-flow left ventricular assist device. N Engl J Med 2009.361: 2241–2251.
5. Feldman D, Pamboukian SV, Teuteberg JJ, et al; International Society for Heart and Lung Transplantation: The 2013 International Society for Heart and Lung Transplantation Guidelines for mechanical circulatory support: Executive summary. J Heart Lung Transplant 2013.32: 157–187.
6. Jung MH, Gustafsson F, Houston B, Russell SD. Ramp study hemodynamics, functional capacity, and outcome in heart failure patients with continuous-flow left ventricular assist devices. ASAIO J 2016.62: 442–446.
7. Zentner D, Cheshire C, Grigg L. Extracardiac conduit Fontan—outcome data in early adulthood. Heart Lung Circ 2018.27: 254–259.
Keywords:

single ventricle; Fontan; CHD; VAD; ramp study

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