The development of advanced technologies of mechanical devices for short- or long-term cardiac support has led to increased adoption of their use by physicians for patients with end-stage cardiac disease. Echocardiography plays a critical role in the management of ventricular assist device (VAD) patients, as noted by a team at Mayo Clinic Arizona who wrote "Echocardiography is fundamental during each stage of patient management, pre-LVAD placement, during LVAD placement, for postoperative LVAD optimization and long-term follow-up" (1). Other physicians at Methodist and Texas Heart in Houston called echo "an ideal modality to monitor patients after LVAD implantation because it is noninvasive, widely available, and can be performed at the bedside" (2). We report here on the use of hTEE to manage a hemodynamically unstable LVAD patient, as well as to optimize LVAD RPM settings.
One critical part of VAD management is controlling the flow rate by adjusting the RPM setting to achieve optimal perfusion. Imaging the LV and RV by echo is the most efficient way to do this. In the case of the longer-term LVAD's such as the HeartMate II, the relationship between RPM and flow is complicated, and the standard technique of estimating flow from LVAD power consumption (3) can be challenging. For example, an increase in power consumption might represent an increase in flow, an increase in afterload, or an obstruction. In addition, the RV in heart failure patients may need time to adapt to increased RV preload generated by LVAD flow. For that reason, it is important to dynamically assess and optimize LVAD RPM settings during the post-operative period while the RV recovers and TEE is very often used to facilitate this. At Newark Beth Israel, a TEE is done on POD#1 and usually again on POD#2 or #3. The changes in volume status that normally occur in the first 48-72 hours postoperatively often require adjustment of RPM's. TEE has also been invaluable to rule out tamponade or RV failure in LVAD patients.
A miniaturized TEE transducer (ImaCor hTEE), the size of an NGT, which can remain indwelling for up to 72 hours to provide continuous imaging at the bedside, offers the potential of on-demand TEE-guided management of VAD patients and replaces the need for repeated insertion of a much larger standard TEE probe. Many, if not most, centers do not have the availability of emergency TEE's during nights and weekends, thus lacking a critically important and rapid way to diagnosis potential life-threatening conditions such as tamponade or worsening RV failure in LVAD patients. Three recent studies (4-6) have shown that hTEE provides a diagnostic yield similar to that of conventional TEE (7,8).
We report here on the use of hTEE to manage a hemodynamically unstable LVAD patient, as well as to optimize LVAD RPM settings.
The patient, a 66 year-old male with a history of dilated cardiomyopathy, NYHA class IIIb/IV, Status IB on UNOS heart transplant waitlist, was on home continuous inotrope therapy (milrinone) for three years. He was admitted in low-output failure, BP 80/60, HR 110, lower extremity 3+ edema. Swan-Ganz catheter inserted with following results: PA pressures 56/35, wedge 25, CVP 18, mixed venous O2 saturation 44%. He received an IABP and dobutamine and lasix were added to his medical regimen. Mixed venous O2 saturation increased only slightly to 50%, PA pressures reduced to 49/30, CVP 16. A HeartMate II LVAD was implanted as bridge to transplantation. Nitric oxide initiated in OR. Initial speed adjustments were done in the OR, immediately post-implant, under intra-operative TEE guidance. Mean arterial pressure 70 (on non-pulsatile LVAD), PA pressures (on nitric oxide) 34/19, CVP 12.
Ten hours post-op, around 11:00 pm, CVP rose to 22, PA pressures 38/20, urine output dropped to 15-20 cc/hr. Concerns were tamponade (requiring surgical re-exploration) vs. RV failure (requiring adjustment of drips or RVAD). An ImaCor hTEE probe was inserted for immediate visualization, and revealed tamponade. Patient returned to OR for evacuation of clot. The ImaCor probe was left in place, since the patient would require routine repeat echo on POD#1 to re-adjust RPM's under TEE guidance. Repeat hTEE imaging led us to increase speed from 8400 RPM to 9000 RPM in stages, improving septal position and optimizing flow (Figure 1).
Figure 1 (Cineloops above). hTEE-guided speed adjustments. Note absence of septal shift at final speed of 9000 RPM.
The ImaCor TEE system provided immediate visualization at a critical point in the immediate postop course, when conventional TEE was not available, and further provided a small indwelling alternative for future echo imaging without the need to re-insert the much larger conventional TEE probe.
- Mookadam F, Kendall CB, Wong RK, Kalya A, Warsame T, Arabia FA, Lusk J, Moustafa S, Steidley E, Quader N, Chandrasekaran K. Left ventricular assist devices: physiologic assessment using echocardiography for management and optimization. Ultrasound Med Biol. 2012;38:335-45. doi: 10.1016/j.ultrasmedbio.2011.11.009.
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- Lund LH, Gabrielsen A, Tirén L, Hallberg A, El Karlsson K, Eriksson MJ. Derived and displayed power consumption, flow, and pulsatility over a range of HeartMate II left ventricular assist device settings. ASAIO J. 2012 May-Jun;58(3):183-90. doi: 10.1097/MAT.0b013e3182496d9a.
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