Changing the Carburetor Without Changing the Plugs

Changing the Carburetor Without Changing the Plugs

JACC: HEART FAILURE VOL. 3, NO. 9, 2015 ª 2015 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION ISSN 2213-1779/$36.00 PUBLISHED BY ELSEVIER INC. ...

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JACC: HEART FAILURE

VOL. 3, NO. 9, 2015

ª 2015 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION

ISSN 2213-1779/$36.00

PUBLISHED BY ELSEVIER INC.

http://dx.doi.org/10.1016/j.jchf.2015.07.001

EDITORIAL COMMENT

Changing the Carburetor Without Changing the Plugs The Intersection of Stock Car Racing With Mechanically Assisted Circulation* Joseph G. Rogers, MD

T

his Editorial Comment is dedicated to those

survival and symptoms in Stage D heart failure

“who think the last four words of the national

with reduced ejection fraction (HFrEF) coupled

anthem are ‘Gentlemen, start your engines’”

with a shortage of suitable donors and a growing

(Jeff Foxworthy) (1).

heart failure population has fueled exponential

Summer in the South is filled with sweltering

growth in left ventricular assist device (LVAD) im-

heat, the sweet smell of magnolias, lazy summer

plantation (2). Registry and clinical trial data have

weekends, and afternoons at the racetrack watching

demonstrated

well-tuned automobiles run at breakneck speeds in

support live longer, with better quality of life and

such proximity that a driver with an extended arm

submaximal exercise performance, when treated

could easily touch an adjacent car. Although many

with LVAD than would be predicted with ongoing

that

patients

requiring

inotropic

view stock car racing as a testosterone-infused,

medical therapy (2,3). Contemporary LVADs have

estrogen-tolerated

of

a rotary design that moves blood continuously

men who attempt to relive youthful aspiration, I

through the pump and typically empty the left

have developed a deep appreciation for the complex

ventricle

man–machine interplay that results in winning a

opening. As a result, pulse pressure is minimized

race.

The

sport

competitive

composed

advantage

primarily

in

stock

sufficiently

to

minimize

aortic

valve

car

and often undetectable using noninvasive tech-

racing goes to the team that most effectively in-

niques. However, despite near normalization of

tegrates a skilled driver, the best car setup, fuel

central hemodynamics with LVAD, exercise perfor-

strategy, teamwork in the pits, and subtle engine

mance does not return to the level of healthy,

nuances that provide a little more speed than

age-matched controls, and continuous flow (CF)

the competition. It is only in the optimization of

LVAD patients have a persistent risk of vascular

these components that the car achieves maximal

adverse events, including mucosal bleeding and

performance.

stroke, suggesting lingering abnormalities in vas-

Over the past decade, mechanically assisted cir-

cular regulation.

culation has earned an accepted position in the

SEE PAGE 703

treatment of advanced heart failure. The limitations of medical and electrical therapies to improve

In this issue of JACC: Heart Failure, Witman et al. (4) provide important insights into the importance of reduced pulse pressure and potential mechanisms that explain the disconnect among improved cen-

*Editorials published in JACC: Heart Failure reflect the views of the authors and do not necessarily represent the views of JACC: Heart Failure or the American College of Cardiology. From the Division of Cardiology, Duke University School of Medicine,

tral

hemodynamics,

suboptimal

functional

im-

provements, and vascular complications in CFLVAD patients. The authors used flow-mediated vasodi-

Durham, North Carolina. Dr. Rogers has reported that he has no re-

lation to evaluate peripheral vascular function in

lationships relevant to the contents of this paper to disclose.

68 subjects distributed across 4 distinct cohorts:

Rogers

JACC: HEART FAILURE VOL. 3, NO. 9, 2015 SEPTEMBER 2015:712–4

Peripheral Vascular Changes in Continuous Flow LVADs

normal controls, New York Heart Association func-

complication

tional class II HFrEF, New York Heart Association

that has been linked to systemic hypertension with

associated

with

CFLVAD

support

functional class III to IV HFrEF, and patients on a

mean arterial blood pressure >90 mm Hg, a level

CFLVAD. They hypothesize that pulsatility would

that would not typically be concerning in non-VAD

decreases across the heart failure continuum with

patients (5). Loss of appropriate cerebral vaso-

the lowest detectable pulsatility in the CFLVAD

regulation may also be implicated in hemorrhagic

cohort and that pulsatility reduction would be

stroke.

correlated with progressively abnormal vascular

This study has a few noteworthy limitations.

physiology. This interesting model addresses the role

First, study patients had a burden of comorbid

of pulse pressure in vascular health and has the

conditions, including hypertension, hyperglycemia,

potential to provide insights about residual func-

and hyperlipidemia, that predispose to atheroscle-

tional limitations and vascular complications asso-

rosis and abnormal vasoregulation. Second, and

ciated with current LVAD technology.

perhaps more important, patients were maintained

The control group was selected to have no

on prescribed medications at the time of the study,

known cardiovascular disease and was not taking

including

prescription medications. The majority of HFrEF

the vasoregulated response. Third, there is an

patients had underlying ischemic heart disease,

assumption

severe ventricular dysfunction, and were more likely

normal central hemodynamics at the time of this

to have abnormal glycemic control. The patient

study, although this was not proven in the con-

groups had lower mean cholesterol values, although

text of this trial. Finally, there is no definitive

nearly 70% were taking a statin at the time of the

linkage of altered vascular response to clinical

flow

events or exercise performance in this patient

velocity, and shear rates were similar across the

cohort, leaving only inference about the clinical

study cohorts. A progressive decline in pulsatility

implications.

study.

Baseline

brachial

artery

diameter,

medications that

that

may

device-supported

have

altered

patients

had

Winning at the race track is in many ways similar

was observed in the heart failure patients (control > HFrEF II > HFrEF III-IV > CFLVAD). The proto-

to

typical vasodilatory response to transient arterial

assisted circulation. Success is a highly dependent

occlusion was progressively attenuated as heart

on a complex interplay of factors, some of which

failure advanced and was most abnormal in the

can be controlled and others that cannot. It requires

CFLVAD cohort. The investigators also demonstrate

integration of man and machine, a constant reas-

that the extent of normal vasodilatory response to

sessment of components, and new approaches to

arterial occlusion was dependent on the degree

old challenges. We have reached a point in me-

of pulsatility.

chanically

achieving

clinical

assisted

benefit

circulation

with

mechanically

where

the

new

This study has several intriguing implications.

devices reliably pump blood for prolonged periods

Peripheral vascular adaptations to heart failure may

of time. We are left with the onerous task of un-

plausibly

exercise

derstanding the impact of minimally pulsatile flow

response, muscle metabolism, and end-organ func-

on long-term outcomes, particularly those affecting

tion. Leveraging the novel circulatory characteris-

the vasculature. Junior Johnson, one of the more

be

implicated

in

abnormal

tics of CFLVADs and creating a human model

famous stock car racers in history, once said, “If

of progressive pulse pressure reduction, the in-

you ain’t cheatin,’ you ain’t tryin’ ” (6). In fact,

vestigators of this study have identified pulse

Mr. Johnson was notorious for making minor illegal

pressure as an important mediator of vascular

alterations in his car so the inspectors would stop

dysfunction in chronic heart failure. In addition,

looking and not find the more egregious changes.

perhaps a portion of the observed vascular adverse

Similarly, we need to search for subtle and overt

events that occur in CFLVAD patients are related

biological and physiological changes associated with

to alterations in normal vasoregulation. For ex-

CFLVAD that might serve as targets to minimize

ample, mucosal arteriovenous malformations are

risk

a common cause of post-operative bleeding in

performance.

and

assist

supported

patients

reach

peak

CFLVAD patients, and it has been postulated that chronic mucosal ischemia plays a role. It is plau-

REPRINT REQUESTS AND CORRESPONDENCE: Dr.

sible that abnormal vasoregulation of splanchnic

Joseph G. Rogers, Duke University School of Medi-

resistance arterioles plays a role in that phenome-

cine, Box 3034 DUMC, Durham, North Carolina 27710.

non. Hemorrhagic stroke is a devastating vascular

E-mail: [email protected].

713

714

Rogers

JACC: HEART FAILURE VOL. 3, NO. 9, 2015 SEPTEMBER 2015:712–4

Peripheral Vascular Changes in Continuous Flow LVADs

REFERENCES 1. Foxworthy J. Available at: www.jefffoxworthy. com. Accessed July 2015.

advanced heart failure patients. J Am Coll Cardiol 2010;55:1826–34.

2. Kirklin JK, Naftel DC, Pagani FD, et al. Sixth INTERMACS annual report: a 10,000-patient database. J Heart Lung Transplant 2014;33: 555–64.

4. Witman MAH, Garten RS, Gifford JR, et al. Further peripheral vascular dysfunction in heart failure patients with a continuous-flow left ventricular assist device: the role of pulsatility. J Am Coll Cardiol HF 2015;3:703–11.

3. Rogers JG, Aaronson KD, Boyle AJ, et al. Continuous flow left ventricular assist device improves functional capacity and quality of life of

5. Teuteberg JJ, Slaughter MS, Rogers JG, et al. The HVAD left ventricular assist device: risk

factors for neurologic events and preventative mitigation strategies. J Am Coll Cardiol HF 2015. in press. 6. Johnson J. Bleacher Report. Available at: www. bleacherreport.com. Accessed July 2015.

KEY WORDS endothelial function, heart failure, mechanically assisted circulation