Research ArticleValidating Left Ventricular Filling Pressure Measurements inPatients with Congestive Heart Failure: CardioMEMS™Pulmonary Arterial Diastolic Pressure versus Left Atrial PressureMeasurement by Transthoracic Echocardiography

Sunit Tolia , Zubair Khan, Gunjan Gholkar, and Marcel Zughaib

Department of Cardiology, Providence-Providence Park Hospital, Michigan State University College of Human Medicine,16001 W. Nine Mile Road, Southfield, MI 48075, USA

Correspondence should be addressed to Sunit Tolia; toliasunit@gmail.com

Received 7 May 2018; Accepted 20 June 2018; Published 15 July 2018

Academic Editor: David J. Chambers

Copyright © 2018 Sunit Tolia et al. 'is is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background. Routine ambulatory echocardiographic estimates of left ventricular (LV) filling pressures are not cost-effective andare occasionally fraught with anatomic, physiologic as well as logistical limitations. 'e use of implantable hemodynamic devicessuch as CardioMEMSHeart Failure (HF) System has been shown to reduce HF-related readmission rates by remote monitoring ofLV filling pressures. Little is known about the correlation between CardioMEMS and echocardiography-derived estimates ofcentral hemodynamics. Methods. We performed a prospective, single-center study enrolling seventeen participants with NewYork Heart Association functional class II-III HF and preimplanted CardioMEMS sensor. Simultaneous CardioMEMS readingsand a limited echocardiogram were performed at individual clinic visits. Estimated left atrial pressure (LAP) by echocardiogramwas calculated by the Nagueh formula. Linear regression was used as a measure of agreement. Variability between methods wasevaluated by Bland–Altman analysis. Results. Mean age was 74± 9 years; 59% (10/17) were males. LV systolic dysfunction waspresent in 76% (13/17) of subjects. Mean PAdP was 18± 4mmHg and 19± 5mmHg for CardioMEMS and echocardiographic-derived estimates, respectively, with a significant correlation between both methods (r2 � 0.798, p≤ 0.001). Conclusions. Ourstudy illustrates a direct linear correlation between PAdPmeasured by CardioMEMS and simultaneous measurement of LV fillingpressures derived by echocardiography.

1. Introduction

Congestive heart failure (CHF) impacts more than sixmillion Americans. It is the admission diagnosis for morethan one million hospitalizations annually and also accountsfor the highest readmission rates [1, 2]. 'e socioeconomicburden associated with the management of heart failure isover $30 billion a year and is expected to exceed $70 billionannually by 2030 [3].

Increase in left atrial pressure (LAP) occurs earlier priorto any symptoms in the hemodynamic cascade of events thateventually leads to heart failure exacerbation [4]. Echocar-diography is essential in evaluating the LAP; however, incertain conditions, the true estimate of LAP is limited by the

presence of anatomical and physiological parameters [5]. Insuch circumstances, E/e’ or Nagueh formula may not be thebest method to calculate the LAP or pulmonary capillarywedge pressure (PCWP). In such instances, other diastologyparameters such as isovolumetric relaxation time (IVRT) orIVRT/TE-e’ ratio are utilized to measure LAP. Furthermore,serial ambulatory evaluations by echocardiography are notonly impractical but are also not cost-effective. Pressure-guided therapy is a novel strategy in the management ofCHF which allows clinicians to proactively manage pa-tients before they decompensate and require hospitaliza-tion. 'e CardioMEMS Heart Failure (HF) System is theonly FDA approved implantable hemodynamic device, andprovides real-time pulmonary artery (PA) hemodynamic

HindawiCardiology Research and PracticeVolume 2018, Article ID 8568356, 6 pageshttps://doi.org/10.1155/2018/8568356

data. Earlier investigations have reported a correlationbetween the standard PA-catheter measurements andechocardiography-derived estimates of pulmonary arterysystolic pressure (PAsP) with CardioMEMS data [6]. Weaimed to explore the agreement between simulta-neous readings of pulmonary artery diastolic pressure(PAdP), a direct estimate of PWCP and LAP (assuming nodiastolic pulmonary pressure gradient), obtained by theCardioMEMSHF system and noninvasive echocardiography-derived estimates of central hemodynamics in compensatedHF patients.

2. Methods

2.1. Study Design. We prospectively enrolled seventeenpatients with a history of CHF and preimplanted Car-dioMEMS HF device. Patients with presence of mitralprosthesis, severe mitral annular calcification, and perma-nent atrial fibrillation were excluded. Simultaneous Car-dioMEMS readings and a limited echocardiogram wereperformed at individual clinic visits to evaluate the agree-ment between PAdP and PAsP via CardioMEMS andechocardiography-derived estimates of LAP. 'e study wasapproved by the local institutional review board. All subjectsprovided an informed consent.

2.2. Data Collection. Subjects were brought in for a routineclinic visit. After initial clinical assessment for volume status,a limited echocardiogram was performed by one technicianusing a Philips Sonos 5500 with a 3.2MHz transducer (PhilipsMedical Systems, Andover, MA), and three CardioMEMSreadings were obtained and averaged. 'e limited echocar-diogram included a parasternal long axis, right ventricularinflow and outflow, apical four chambers, and subcostal viewsfor the inferior vena cava. All the four valves were pulsed toevaluate for stenotic and regurgitant lesions. Mitral inflowvelocities were obtained from an apical four chamber viewusing the pulse wave Doppler. 'e sample volume was placed1–3mm between the mitral leaflet tips during diastole. 'einflow velocities were measured at end-expiration witha sweep speed of 100m/s.'e tissueDoppler at themedial e’ andlateral e’ annulus was pulsed from an apical four chamber view.A sniff test was also performed at the time of evaluating theinferior vena cava (IVC) for estimation of right atrial pressure(RAP) [7]. PAsP was then calculated via the tricuspid re-gurgitation jet velocity (VTR) as follows: PAsP� 4(VTR)2+RAP.Mitral inflow velocity (E) and septal and lateral annular (e’)velocities were averaged to calculate the E/e’ ratio. EstimatedLAP was then calculated by taking the ratio of E/e’ andapplying the Nagueh formula (LAP� 1.24× (E/e’) + 1.9) [8].Right heart catheterization tracings at the time of Car-dioMEMS implantation for all subjects were reviewed toassess for agreement between the PA pressure readings andpresence of diastolic pulmonary gradient (DPG) defined asthe difference between invasive PAdP and mean PCWP.PAdP correction was performed for DPG≥ 7mmHg at thetime of CardioMEMS implant to adjust for presence ofconcomitant pulmonary vascular disease [9].

2.3. Statistical Analysis. All statistical analyses were per-formed using IBM SPSS, version 21.0. Summary statistics arepresented as N (%) for categorical variables; continuousvariables are presented as mean± SD. Linear regressionanalysis was used for the comparison of PA pressures ob-tained with CardioMEMS and echocardiographic-derivedmeasurements. Variability between the methods wasexpressed relative to the average PA pressures plus 2 SDs byBland–Altman analysis. Significance was determined as a p

value< 0.05.

3. Results

Baseline demographic, anthropomorphic, and clinical his-tory are presented in Table 1. Baseline medical therapy forCHF at the time of assessment is presented in Table 1. Twosubjects had baseline DPG≥ 7mmHg (8 and 11mmHg)noted at the time of CardioMEMS implant requiring PAdPcorrection. All subjects were euvolemic by clinical exam andin normal sinus rhythm at the time of simultaneous echo-cardiographic assessment and CardioMEMS readings. Av-eraged invasive PA pressures from CardioMEMS implantdate and simultaneous echocardiographic-derived andCardioMEMS hemodynamic data are presented in Table 2.Echocardiographic-derived LAPwas higher compared to thePAdP reading from CardioMEMS (1.4± 2.1mmHg,p � 0.015) with no significant difference between estimatedPAsP readings (0.49± 1.7mmHg, p � 0.264). Linear re-gression and agreement plots for PAdP and PAsP fromCardioMEMS and echocardiogram as a function of average

Table 1: Baseline characteristics.

N � 17Age (mean± SD) 74± 9Gender (n, %)

Male 10 (59%)BMI (mean± SD) 31.7± 6.3Smoking (n, %)

Never smoker 7 (41%)Current smoker 1 (6%)Former smoker 9 (53%)

CHF categoryHFrEF 15 (75%)HFpEF 5 (25%)

Hypertension (n, %) 17 (100%)Hyperlipidemia (n, %) 17 (100%)Diabetes mellitus (n, %) 10 (59%)Coronary artery disease (n, %) 14 (82%)Peripheral arterial disease (n, %) 3 (18%)Atrial fibrillation/other arrhythmias (n, %) 6 (35%)Chronic lung disease (n, %) 9 (53%)Chronic kidney disease (n, %) 4 (23%)Baseline medical therapy for congestive heart failureBeta-blockers (n, %) 17 (100%)ACE-I or ARB (n, %) 7 (41%)ARB/neprilysin inhibitor (n, %) 8 (47%)Aldosterone receptor blocker (n, %) 12 (71%)Diuretics (n, %) 17 (100%)Other vasodilators (n, %) 2 (12%)Digoxin (n, %) 3 (18%)

2 Cardiology Research and Practice

measurements are shown in Figures 1 and 2, respectively.A significant correlation was observed for the PAdP(r2 � 0.798, p≤ 0.001) and PAsP (r2 � 0.952, p≤ 0.001)measurements between both methods. Using Bland–Altman analytic methods, the bias for the echocardio-graphic estimates of the PAdP and PAsP was −0.12mmHgand 0.49mmHg with 95% limits of agreement rangingfrom +3.37 to −3.62mmHg and +3.91 to −2.93mmHg,respectively. Doppler echocardiography was inaccurate(defined as being greater than ±5mmHg of the Car-dioMEMS measurement) in <1% (1/17) of cases for bothPAdP and PAsP with PAdP being overestimated by7mmHg and PAsP underestimated by 6mmHg byechocardiography in the aforementioned instances.

4. Discussion

Acute decompensated heart failure (ADHF) is associatedwith abnormal hemodynamics especially left ventricularfilling pressure and cardiac output. While invasive hemo-dynamic monitoring using a pulmonary artery catheter inADHF provides useful objective data, its clinical use haslargely fallen out of favor in uncomplicated cases and is notrecommended for routine hemodynamic monitoring inADHF [10]. Echocardiography, on the other hand, is un-arguably the most useful tool for initial assessment of pa-tients with suspected diagnosis and follow-up of CHFallowing for risk-stratification of high-risk patients [11].Progression of heart failure leads to chronic activation ofneurohumoral regulation which promotes increase in atrialnatriuretic peptide, brain natriuretic peptide, angiotensin II,and aldosterone all which contribute to left atrial remodeling[12]. 'ese changes results in diastolic dysfunction whichcan be evaluated by Doppler echocardiography, and itspresence has been associated with an increased all-causemortality [13] and progression on serial assessments sub-sequent development of heart failure [14].

'e use of E/e’ is the most feasible and reproduciblemethod for the estimation of filling pressures and predictiveof normal or abnormal filling pressures when the ratio is <8or >15, respectively [14, 15]. E/e’ may be an unreliable way topredict LV filling pressures in certain clinical settings. For

instance, those with long-standing HFrEF who have un-dergone left ventricular remolding may already have LVdilation and functional mitral regurgitation. 'e functionalmitral regurgitation leads to an increase in transmitral in-flow, the peak E velocity increases on the mitral inflow, andthere is a reduction in the systolic to diastolic (S/D) ratio inthe pulmonary venous flow [16]. In patients with decom-pensated heart failure or with cardiac resynchronizationtherapy, E/e’ shows a poor correlation with intracardiacfilling pressures especially with large LV volumes because ofsignificant mitral regurgitation and wide QRS leading toabnormal septal motion [16]. Furthermore, in cases such asheart transplantation, mitral valve repair or replacement,severe mitral annulus calcification, or mitral stenosis, theannular tissue velocities are affected; therefore, E/e’ is not thebest indicator of LAP estimation [17]. Finally, poor acousticwindows may preclude accurate assessment of transmitralDoppler velocities.

Recognizing the potential limitations of transmitralDoppler velocities for assessment of LAP, the currentAmerican Society of Echocardiography/European Associa-tion of Cardiovascular Imaging guidelines for assessment ofdiastolic dysfunction recommend utilization of PAsP de-rived from VTR as a surrogate marker for LAP in the absenceof pulmonary vascular or parenchymal disease [15]. Again,the accuracy of the Doppler method for PAsP estimation iscontingent upon obtaining the correct peak velocity froma coaxial VTR signal from which the peak pressure can beestimated. A poor quality or noncoaxial signal can fre-quently underestimate the estimated PAsP.'is occurs morethan frequently in patients with severe lung disease wherePAsP estimation should be avoided in the absence of a goodVTR envelope [16]. Chronic elevation in right sided fillingpressures could lead to right ventricular (RV) compensationwith decrease in tricuspid regurgitation and un-derestimation of PAsP [18]. Calculations using the VTRDoppler signal assume that there is no pulmonary valvestenosis andmay be inaccurate in the presence of RV systolicdysfunction. Furthermore, RAP is often overestimated ifIVC measurement is used, leading to overestimation ofPAsP [19].

Serial echocardiographic assessments provide little in-cremental prognostic information over clinical presentationor biomarkers in patients with ADHF [20]. In currentpractice, the role of echocardiography in the management ofdecompensated heart failure patients is limited to evaluationof LV function and regional wall motion abnormality. It isseldom used to guide therapy, and needless to say, moni-toring of serial hemodynamics to prevent heart failurehospitalization is neither cost-effective nor realistic. In 2014,the U.S. FDA approved the CardioMEMS HF system whichis a wireless, battery-free, PA pressure monitoring system.'e device is implanted into a branch of the pulmonaryartery during right heart catheterization and is powered byand interrogated via an external antenna. Pressures appliedto the sensor causes deflections of the pressure-sensitivesurface resulting in a characteristic shift in the resonantfrequency. An external antenna achieves electromagneticcoupling. In the CHAMPION (CardioMEMS Heart Sensor

Table 2: Invasive and noninvasive hemodynamic data fromCardioMEMS implant and simultaneous echocardiographicassessment.

N � 17Invasive hemodynamics at CardioMEMS implantPAsP, mmHg (mean± SD) 49± 16PAdP, mmHg (mean± SD) 21± 7

Hemodynamics by CardioMEMSPAsP, mmHg (mean± SD) 42± 8PAdP, mmHg (mean± SD) 18± 4

Estimated hemodynamics by echocardiogramPAsP, mmHg (mean± SD) 42± 8LAP, mmHg (mean± SD) 19± 5

LAP, left atrial pressure; mPAP, mean pulmonary artery pressure; PAdP,pulmonary artery diastolic pressure; PAsP, pulmonary artery systolicpressure.

Cardiology Research and Practice 3

Allows Monitoring of Pressure to Improve Outcomes inNYHA Class III Heart Failure Patients) trial, remotemonitoring and titration of diuretic and vasodilator therapybased on patient-transmitted readings of PAdP from theCardioMEMS HF system showed a 37% reduction in heartfailure-related hospitalizations (HR 0.63, 95% CI 0.52–0.77,p< 0.0001) [21].

'ere is only limited data on simultaneous assessment ofPA pressures derived from the CardioMEMS device andechocardiographic estimates. Verdejo et al. performed serialassessments in 12 subjects to assess correlation betweenwireless PA pressure monitoring using CardioMEMS withSwan–Ganz catheter and echocardiographic PA pressuremeasurements [6]. CardioMEMS readings and echocardi-ography were performed at 2, 14, 30, 60, and 90 days whileSwan–Ganz catheterization was performed at 0 and 60 days.'e study showed an excellent correlation between allmethods with high reproducibility and low interob-server variability between measurements. PAsP and PAdP

measurements between the CardioMEMS device andSwan–Ganz catheter showed a significant correlation(r2 � 0.96 and 0.88 at baseline, r2 � 0.90 and 0.48 follow-up, p≤ 0.01), with a mean difference of 6.2± 4.5 and −1.6±6.8mmHg, respectively. PAsP measurements betweenCardioMEMS and echocardiographic-derived estimate alsohad a significant correlation (r2 � 0.75, p≤ 0.01) witha mean difference of −2.6± 11mmHg. Echocardiographydetermination of PAdP in their study was only feasible in 2patients due to technical reasons and hence was notreported.

Our study, for the first time, reports simultaneoushemodynamic readings from CardioMEMS andechocardiography-derived estimates of both PAsP andPAdP as a surrogate marker for LAP. Similar to the findingsby Verdejo et al., there was a significant correlation betweenall CardioMEMS and Swan–Ganz catheter PA pressurereadings at the time of implant amongst the enrolled patientson retrospective review of all tracings (data not presented).

8

6

4

2

0

Card

ioM

EMS

PAdP

-ECH

O L

AP

(E/e

’+4)

(mm

Hg)

–2

–4

–6

–80 10 20

Averaged PAdP from CardioMEMS andECHO LAP (E/e’ + 4) (mmHg)

30 40

+1.96 SD3.37

Mean–0.12

–1.96 SD–3.62

(a)

30

20

10

00 5 10 15

Averaged PAdP from CardioMEMS (mmHg)20 25 30

Estim

ated

LA

P by

ECH

O(E

/e’+

4) (m

mH

g)

r2 = 0.798, p ≤ 0.001

(b)

Figure 1: Bland–Altman analysis (a) and linear correlation (b) between CardioMEMS-derived pulmonary artery diastolic pressure (PAdP)and echocardiography-estimated left atrial pressure (LAP) by Nagueh formula (estimated LAP� 1.24× (E/e’) + 1.9).

Card

ioM

EMS

PAsP

-ECH

O es

timat

edPA

sP (m

mH

g)

8

6

4

2

0

–2

–4

–6

–810 20 30 40

Averaged PAsP from CardioMEMSand ECHO PAsP (mmHg)

50 60 70

+1.96 SD

–1.96 SD–2.93

3.91

Mean0.49

(a)

70

60

50

40

30

Estim

ated

PA

sP b

y EC

HO

(mm

Hg)

2020 30 40

Averaged PAsP by ECHO (mmHg)50 60 70

r2 = 0.952, p ≤ 0.001

(b)

Figure 2: Bland–Altman analysis (a) and linear correlation (b) between CardioMEMS-derived pulmonary artery systolic pressure (PAsP)and echocardiography-estimated PAsP derived from tricuspid regurgitation jet velocity.

4 Cardiology Research and Practice

Of note, there were very few patients who had normal LVfillingpressures because the cohort included patients with baselineNYHA class III heart failure who qualified for CardioMEMSimplantation (Figure 1). Likewise, there was good correlationbetween CardioMEMS and echocardiographic-derived esti-mates of PAsP. While none of the subjects in our cohorthad primary pulmonary hypertension, evidence of rightventricular dilatation/dysfunction or evidence of pulmonicstenosis, 9 (out of 17) subjects did have a history of em-physematous lung disease with 4 of them being on homeoxygen therapy which, as stated above, could have poten-tially underestimated the echocardiographic-derived PAsP.'is was indeed noticed in one of these subjects in ourcohort (outlier, Figure 2(a)) with an inadequate VTR signaland evidence of enlarged right atrium, signifying chronicelevation in right-sided filling pressures. In addition, therewas presence of baseline DPG in 2 subjects signifyingpresence of mixed pulmonary hypertension. While Verdejoet al. could not reliably report echocardiography-derivedPAdP, our study specifically aimed to look at its comparisonwith the CardioMEMS data. While there are currently noguidelines available for DPG correction for an accurateassessment of derived LAP, we used an acceptable DPGcutoff of 7mmHg. All 17 subjects had reliable Doppler datafor accurate assessment of estimated LAP with significantcorrelation seen between both methods.

5. Conclusion

Congestive heart failure is a syndrome that impacts millionsof Americans on a daily basis and its management continuesto evolve so that more patients are symptom-free, heart-failure hospitalization decreases, and socioeconomic burdenassociated with the management of heart failure is reduced.Chronic heart failure management is transitioning fromsymptom-guided therapy to pressure-guided therapy be-cause the hemodynamic changes occur well in advance. 'eCardioMEMS HF system is the only FDA-approved devicethat has shown to reduce hospital readmission for heartfailure. PAdP has now been established as the best guide formonitoring and titration of medications in ambulatory HFpatients. Our study, for the first time, illustrates a directlinear correlation between PAdP measured by the Car-dioMEMS HF system and simultaneous measurement ofechocardiography-derived estimated of LAP. While echo-cardiography remains as an invaluable tool in our clinicalpractice, one must be aware of the nuances associated withDoppler-derived estimates of filling pressures. Car-dioMEMS, in appropriately selected patients, is a valuabletool in a cardiologist’s armamentarium to accuratelymonitor and optimize filling pressures in patients with CHFand reduce the risk of hospitalization.

Abbreviations

ADHF: Acute decompensated heart failureCHF: Congestive heart failureDPG: Diastolic pressure gradientFDA: Food and Drug Administration

HF: Heart failureIHD: Implantable hemodynamic deviceIVC: Inferior vena cavaLAP: Left atrial pressureLV: Left ventricleNYHA: New York Heart AssociationPA: Pulmonary arteryPAdP: Pulmonary artery diastolic pressurePAsP: Pulmonary artery systolic pressurePCWP: Pulmonary capillary wedge pressureRAP: Right atrial pressureRV: Right ventricleVTR: Tricuspid regurgitation velocity.

Conflicts of Interest

'e authors declare that they have no conflicts of interest.

Authors’ Contributions

'e authors take responsibility for all aspects of the re-liability and freedom from bias of the data presented andtheir discussed interpretation.

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