The Evolution of Temporary Percutaneous Mechanical Circulatory Support Devices: a Review of the Options and Evidence in Cardiogenic Shock

Imaging for Temporary Mechanical Circulatory Support Devices

Heart failure is an important cause of mortality and morbidity in the world. Changes in organ allocation for solid thoracic (lung and heart) transplantation has increased the number of patients on mechanical circulatory support. Temporary mechanical support devices include devices tht support the circulation directly or indirectly such as extracorporeal membrane oxygenation (ECMO) and temporary support for right-sided failure, left-sided failure or biventricular failure. Most often, these devices are placed percutaneously and require either guidance with echocardiography, continuous radiography (fluoroscopy) or both. Furthermore, these devices need imaging in the intensive care unit to confirm continued accurate placement. This review contains the imaging views and nuances of the temporary assist devices (including ECMO) at the time of placement and the complications that can be associated with each individual device.

A Scalable Approach to Determine Intracardiac Pressure From Mechanical Circulatory Support Device Signals

OBJECTIVE

Effective mechanical circulatory support (MCS) relies on cardiac function measures to guide titration. Left ventricular end diastolic pressure (LVEDP) is a useful measure that is indirectly estimated using pulmonary artery catheters (PACs). PACs require additional intervention and provide intermittent and unreliable estimations. MCS device signals can estimate LVEDP but are prone to inter-device variability and require rigorous specialized characterization. We present a scalable and implementable approach to calculate LVEDP continuously using device signals.

METHODS

LVEDP was calculated from MCS device measured aortic pressure and motor current, which approximates the pressure head between the aorta and left ventricle. This motor current-pressure head relationship is device-specific but approximated using existing flow calibration and assumed physiologic relationships. Performance was evaluated with comparison from direct measurement of LVEDP in a series of acute animal models.

RESULTS

LVEDP measures (n = 178,279) from 18 animals had good correlation (r = 0.84) and calibration (Bland-Altman limits of agreement -7.77 to 7.63 mmHg; mean bias -0.07 ± 0.02 mmHg). The total mean error prediction interval was -3.42 to 3.32 mmHg and RMS error was 3.85 mmHg.

CONCLUSION

LVEDP can be continuously calculated using device signals without specialized characterization. Calculated LVEDP values improved upon PAC estimations and were found using a scalable and manufacturer-accessible method.

SIGNIFICANCE

This method improves upon existing LVEDP measures without the need for rigorous characterization, external calibration, or additional intervention; this allows widescale deployment of continuous LVEDP measurement for patients on MCS and demonstrates key considerations necessary to translate research-grade technologies.

Mechanical Circulatory Support for High-Risk Pulmonary Embolism

Temporary mechanical circulatory support (MCS) devices have a role in treating high-risk patients with pulmonary embolism with cardiogenic shock. Mechanical circulatory device selection should be made based on center experience and device-specific features. All current devices are effective in decreasing right arterial pressure and providing circulatory support of 4 to 5 L/min. The pulmonary artery pulsatility index may prove to be an unreliable method to assess right ventricular function. Careful clinical evaluation on an individual patient basis should determine the need for MCS.

Comparing Percutaneous to Open Access for Extracorporeal Membrane Oxygenation in Pediatric Respiratory Failure

OBJECTIVES

Evaluate trends in method of access (percutaneous cannulation vs open cannulation) for pediatric extracorporeal membrane oxygenation and determine the effects of cannulation method on morbidity and mortality.

DESIGN

Retrospective cohort study.

SETTING AND SUBJECTS

The Extracorporeal Life Support Organization's registry was queried for pediatric patients on extracorporeal membrane oxygenation for respiratory failure from 2007 to 2015.

INVERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 3,501 patients identified, 77.2% underwent open cannulation, with the frequency of open cannulation decreasing over the study period from approximately 80% to 70% (p < 0.001). Percutaneous cannulation patients were more commonly male (24.2% vs 21.5%; p = 0.01), older (average 7.6 vs 4.5 yr; p < 0.001), and heavier (average 33.0 vs 20.2 kg; p < 0.001). Subset analysis of patients on venovenous extracorporeal membrane oxygenation revealed higher rates of mechanical complications due to blood clots (28.9% vs 22.6%; p = 0.003) or cannula problems (18.9% vs 12.7%; p < 0.001), cannula site bleeding (25.3% vs 20.2%; p = 0.01) and increased rates of cannula site repair in the open cannulation cohort. Limb related complications were not significantly different on subset analysis for venovenous extracorporeal membrane oxygenation patients stratified by access site. Logistic regression analysis revealed that method of access was not associated with a difference in mortality.

CONCLUSIONS

The proportion of pediatric patients undergoing percutaneous extracorporeal membrane oxygenation cannulation is increasing. Mechanical and physiologic complications occur with both methods of cannulation, but percutaneous cannulation appears safe in this cohort. Further analysis is needed to evaluate long-term outcomes with this technique.

Prolonged veno-arterial extracorporeal life support for cardiac failure

OBJECTIVES

In intractable cardiogenic shock, extracorporeal life support frequently is the last treatment option. Outcomes of prolonged veno-arterial extracorporeal life support for cardiac failure are poorly defined.

METHODS

We retrospectively analyzed 10 patients (4 females, age = 36 ± 16 years) who underwent prolonged extracorporeal life support (≥7 days) from December 2015 to March 2017 for cardiogenic shock. The primary endpoint was survival to hospital discharge.

RESULTS

Etiologies included ischemic cardiomyopathy with non ST-segment elevation myocardial infarction (n = 1), dilated (n = 3), hypertrophic (n = 1), postpartum cardiomyopathy (n = 1), and others (n = 4). Heart failure was left or biventricular in 80.0% (left ventricular ejection fraction = 15.6 ± 5.5%). Among the 10 patients, 80.0% underwent femoral and 20.0% central cannulation, 40.0% required changes in the cannulation strategy, and 80.0% underwent left ventricular venting. No technical malfunctions occurred, but 50.0% required circuit exchanges for thrombus formation. 80.0% suffered from infections. 60.0% could be decannulated after 717 ± 830 (168-2301) h of support, and survival to hospital discharge was 40.0%. Longest follow-up available is 160 ± 175 (12-409) days after discharge, with 30.0% alive and in satisfying functional condition.

CONCLUSION

Prolonged veno-arterial extracorporeal life support for cardiac failure is feasible with low technical complication rates. Survival rates are acceptable, yet inferior to short-term support. We observed a shift from initial shock-related complications to infections during prolonged support. Since recovery and thus weaning is rather unlikely after a prolonged need for extracorporeal life support, this form of support should be limited to centers offering the full spectrum of interdisciplinary cardiac care including ventricular assist device implantation and transplantation.

Options for temporary mechanical circulatory support

Temporary mechanical circulatory support (MCS) refers to a group of devices generally used for less than 30 days to maintain adequate organ perfusion by compensating for a failure of the pumping mechanism of the heart. The increased availability and rapid adoption of new temporary MCS strategies necessitate physicians to become familiar with devices placed both percutaneously and via median sternotomy. This review will examine the different options for commonly used temporary MCS devices including intra-aortic balloon pumps (IABPs), veno-arterial-extracorporeal membrane oxygenation (VA-ECMO), TandemHeart(®) (CardiacAssist, Pittsburg, PA, USA) Impella(®) and BVS 5000(®) (both Abiomed Inc., Danvers, MA, USA), CentriMag(®) and Thoratec percutaneous ventricular assist device (pVAD)(®) (both Thoratec Corporation, Pleasanton, CA, USA). A specific emphasis will be made to describe relevant mechanisms of action, standard placement strategies, hemodynamic effects, relevant contraindications and complications, and important daily management considerations.