Hypertension Journal

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Echocardiography in Hypertension
  JOHTN
REVIEW ARTICLE
Echocardiography in Hypertension
Prakash N. Nair
Consultant Cardiologist and Professor of Medicine, PRS Hospital, Thiruvananthapuram, Kerala, India
Address for correspondence: Dr. Prakash N. Nair, MD(Med), DNB(Cardio), FESC, FSCAI Consultant Cardiologist and Professor of Medicine, PRS Hospital,Thiruvananthapuram, Kerala, India.
E-mail: drprakashnnair@gmail.com
Received: 23-11-2018; Accepted: 05-01-2019
doi: 10.15713/ins.johtn.0142
 
ABSTRACT
Hypertension (HTN) is a treatable risk factor for cardiovascular diseases. Accurate diagnosis of HTN along with the assessment ofcardiovascular risk is essential for proper treatment in hypertensive patients. Echocardiography provides prognostic factors in HTNincluding left ventricular mass, systolic function, diastolic function, left atrial function, and size. Apart from routine echo methods,tissue Doppler, three-dimensional echo, and strain imaging are newer echo techniques in the evaluation of hypertensive patients.Familiarity with routine and newer echo parameters is helpful for risk stratification in HTN.
Keywords: Left ventricular mass, echo parameters, cardiovascular risk
How to cite this article: Nair PN. Echocardiography inHypertension. Hypertens 2019;5(1): 8-13.
Source of support: Nil
Conflict of interest: None
 
 

Introduction

Echocardiography is the simple routine investigation whichprovides information regarding pathophysiology andcomplications of hypertension (HTN). Anatomical andphysiological changes in heart can be detected with thisreproducible imaging technique [Figure 1]. Early target organdysfunction can be detected by echo as a predictor of risk.

Indications of Echocardiography in HTN[1]

  • In patients with mid-diastolic HTN (90-94 mmHg) withno other cardiovascular risk factors or evidence of endorgandamage (including lack of or equivocal signs of theleft ventricular hypertrophy [LVH] on electrocardiography[ECG])
  • The demonstration of LVH by echo is generally an indicationfor medical therapy, while non-pharmacological modalitiesalone can be used if the left ventricle (LV) mass is normal
  • In patients who have no evidence of end-organ damage, whohave either severe or refractory HTN or HTN that is presentin the doctor's office, but not at home or work. The absenceof LVH in this setting suggests either HTN of recent onset orwhite coat HTN. The presence of the latter can be confirmedby ambulatory blood pressure (BP) monitoring
  • Similarly, the presence of significant LVH onechocardiography, with normal clinical BP recordings,mandates ambulatory BP monitoring, to detect maskedHTN
  • In patients with known or suspected concomitant heartdisease in whom the heart disease itself needs furtherevaluation or in whom the type of heart disease might suggesta particular form of antihypertensive therapy. As an example,an angiotensin-converting enzyme inhibitor or angiotensinreceptor blocker would be preferred in a patient with systolicdysfunction or mitral regurgitation
  • In patients who have a bundle branch block on ECG.

 
In contrast, performance of an echocardiography for thepurpose of measuring LV mass is not recommended for theselection of antihypertensive therapy or for the assessment of LVmass in patients without adequate BP control.[1]

The European Society of Cardiology HTN guidelines in 2013mention echocardiography as the second approach after routinehistory, clinical examination, and laboratory tests. Echocardiographydetects LVH, left atrial (LA) dilatation, or associated heart diseases(Class IIb). Canadian HTN Education Programme in 2014suggested echo evaluation in selected patients with HTN. Echo isnot routinely indicated in all hypertensive patients [Table 1 andFigure 2]. If cardiac failure or coronary disease is suspected clinically,LV mass, systolic and diastolic function should be assessed byecho.[2]

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Clinical flow chart for echocardiographic evaluation of hypertension Nair

Echocardiography in Hypertension
Figure 1: Staging of hypertensive heart disease

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Figure 2: Clinical flow chart for echocardiographic evaluation in hypertension

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Nair Clinical flow chart for echocardiographic evaluation of hypertension

Echocardiographic Evaluations

LV Mass[3]

Echo is more sensitive than ECG for the assessment of LVH.Echo helps in cardiovascular risk assessment and in selectionof proper antihypertensive treatment [Figures 3-5]. LV masscan be measured with the equation from the American Societyof Echocardiography, using two-dimensional (2D) linear LVmeasurements [Figure 6].

LV mass = 0.8 × 1.04 × ([LVIDd + PWTd + SWTd] 3-LVIDd 3) + 0.6

(LVID-LV internal diameter - end diastole, PWTd posteriorwall thickness - end diastole, and SWTd Interventricular septalwall thickness - end diastole). Small variations in calculation cancause significant changes in values. Relative wall thickness (RWT),measured as (2 × PWTd)/LVIDd, classifies LVH into concentrictype (RWT > 0.42) or eccentric type (RWT< 0.42). Cutoff levelsof LV mass, suggesting LVH - are 125 g/m2 in men and 110 g/m2 inwomen.[2] Concentric hypertrophy correlated with mortality riskfor patients with suspicion of coronary artery disease (CAD).Three-dimensional (3D) echocardiographic assessment of LVmass correlated well with magnetic resonance imaging (MRI).

Table 1: Clinical indications for echocardiography in hypertension
Echocardiography in Hypertension
RAE: Right atrial enlargement, LAE: Left atrial enlargement,
LVH: Left ventricular hypertrophy, RVH: Right ventricular hypertrophy,
ECG: Electrocardiogram, LBBB: Left bundle branch block


Echocardiography in Hypertension
Figure 3: Effect of LVH on incidence of sudden cardiac death

 
LV Systolic Function

Ejection fraction (EF) can be assessed with modified Simpson'smethod. Normal EF is >55%. Echo suggests evidence of CADalong with the assessment of LV function. 3D echo measurementhas advantages for calculation of LV volumes in patients withregional wall motion abnormalities (RWMA) or LV aneurysms.3D echo correlates well with MRI assessment. 3D echo hassignificant reproducibility. Tissue Doppler imaging (TDI)assesses mitral annular movement. Mitral annular velocity isless in HTN with normal EF. Hence, it predicts subclinical LVsystolic dysfunction. Myocardial function assessment by strainecho has advantages over routine LVEF measurement by echo.Global and regional myocardial functions are well assessed.2D speckle tracking echo assesses myocardial deformation bytracking of natural acoustic markers formed between ultrasoundand myocardium. These markers are described as speckles.Angle independent and multidirectional (longitudinal, radial,and circumferential) strain values can be derived. Inter- andintra-observer variability with 2D strain echo is much less thantissue Doppler assessment. Subclinical target organ damagecan be assessed early. Longitudinal strain is less in patients withHTN, having normal LV systolic function, and it correlates withserum tissue inhibitor of matrix metalloproteinase-1 value, abiomarker for myocardial fibrosis.

Echocardiography in Hypertension
Figure 4: Effect of LV mass on cardiovascular events

Echocardiography in Hypertension
Figure 5: Comparative efficacy of antihypertensive drugs to reduceLV mass

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Clinical flow chart for echocardiographic evaluation of hypertension Nair

Echocardiography in Hypertension
Figure 6: Calculation of LV mass

3D strain echocardiography can assess the motion ofmyocardial speckles. Assessment of the whole LV from a singlevolume data can be done with 3D strain echocardiography.[2]

LV Diastolic Function [Table 2][2]

Echocardiography assesses LV diastolic function. LV fillingpressure is estimated. Increased LA size and volume suggestincreased LV filling pressure. Increased LA diameter was seen in20% of hypertensive patients. Enlarged LA indicates elevated LVfilling pressure and increased LA size and volume correlate withmorbidity and mortality.

Mitral inflow pattern assessed by pulsed-wave Dopplertechnique estimates diastolic dysfunction. Isovolumetricrelaxation time, ratio of E and A velocities, deceleration time ofE velocity, and duration of A wave can be used to assess diastolicdysfunction. However, these velocities can be influenced bymultiple factors including age, heart rate and rhythm, cardiacoutput, mitral annular size, and LA function.

Mitral annular velocity can be assessed by pulsed-waveDoppler of mitral annulus from TDI [Figure 7].

The ratio E/e' can be a good indicator of LA pressure and itis the most feasible marker for estimation of LA filling pressure.This ratio correlates well with LA filling pressure. If E/e' is < 8correlation is better. Ratio >15 indicates elevated LA fillingpressure.

E/e' ratio may not always correlate with LA filling pressure.In patients with systolic heart failure, there is poor correlation. Inpatients with tachycardia, valvular heart disease, and left bundlebranch block, the ratio may be inaccurate.

 
Diastolic stress echo with exercise stress identifieshemodynamic effects of exercise-induced rise in diastolicfilling pressure, as a non-invasive method. Subclinical diastolicdysfunction can be diagnosed in patients having dyspnea.

LA Assessment

LA enlargement is seen in systemic HTN, in the absence ofvalvular heart disease, and it is usually seen along with obesity,LVH, and metabolic syndrome. The LA size is measuredwith parasternal long axis view - end systole at its maximumdimension, avoiding foreshortening. Normal value is 2.7-3.8cm in female and 3.0-4.0 cm in male.[2]

LA volume is measured by 2D echo [Figure 8]. Normalvalue is < 28 ml/m2 and enlarged LA predicts prognosis. Risein LA size and volume indicates diastolic dysfunction in HTNand suggests morbidity and mortality. Volume >34 ml/m2 markspoor prognosis predicting death, heart failure, atrial fibrillation(AF), and ischemic stroke. LA volume does not change fast withtreatment, it is not a good marker of treatment response.

LA strain with strain rate identifies subclinical dysfunction ofatria in HTN.

LA appendage function provides clue of LA function.Reduced function is seen in non-dipper than dipper patientswith HTN. 3D echo also measures size and function of LA.

Associated EchoCharacteristics in HTN[4]

Secondary pulmonary artery pressure (PAH) occurs dueto raised LA pressure being transmitted into pulmonaryvasculature. Heart failure with preserved left ventricular ejectionfraction leads to PAH. Echo measures pulmonary artery pressurewith tricuspid regurgitation (TR) velocity or right ventricularoutflow tract (RVOT) velocity.[2]

PASP=RVSP=RAP + 4 X TR V max2

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Nair Clinical flow chart for echocardiographic evaluation of hypertension

Echocardiography in Hypertension
Figure 7: Left ventricular diastolic function assessment

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Figure 8: Left atrial volume measurement

RVOT acceleration denotes the time from beginning of RVejection to maximum systolic flow velocity. Normal value is140 ms and is reduced in PAH (near 80 ms).

HTN acts as risk factor causing atherosclerosis.Atherosclerotic cardiac involvement is seen during echoevaluation. CAD, ascending aorta dilatation, and aortic valvestenosis or sclerosis may be found. RWMA or LV aneurysmmay be found in CAD patients. Stress echo by dobutamine orexercise is more sensitive for CAD. Ascending aorta dilatationis seen along with increased arterial stiffness and LV mass, inabout 17 % of patients with HTN. Aortic valve calcification isa common finding, suggesting atherosclerosis. Aortic valvesclerosis predicts clinical events.

 
Table 2: Echo parameters for LV Diastolic function (Based onEuropean Society of Cardiology guidelines)[5]
Echocardiography in Hypertension
LA: Left atrium, LV: Left ventricle, RWS: Relative wall thickness

Dipper and Non-dipper BP

BP reduction at night time < 10% suggests non-dipper pattern ofBP. Non-dipper BP pattern is usually seen with high LV mass,reduced LV and RV function. Hence, it predicts cardiovascularevents.

Stress Echocardiography

LVH leads to false-positive results in exercise tests by ECG orsingle-photon emission computed tomography. It does notchange the results of stress echo. Exercise echo is thus a bettermethod to diagnose CAD in patients with HTN.[6]

Acute Chest Pain and HTN[6]

In the setting of equivocal ECG changes and negative biomarker,echo evidence of RWMA indicates acute coronary syndrome(ACS). No RWMA by echo rules out significant ACS and pointstoward HTN as a cause of chest pain. HTN raises intracavitary enddiastolicpressures, which compresses the subendocardial region,inducing ischemia resulting in chest pain, an effect exaggerated bythe presence of LVH. Normalizing BP will lead to relief of chest painand save unnecessary diagnostic workup for ACS in emergency.Bedside echo easily diagnoses aortic stenosis in the presence ofchest pain and high BP may reveal dissection of aorta involvingascending aorta and its extent. In young hypertensive patients, echocan reveal coarctation of aorta or aortoarteritis.

Arrhythmias and HTN[6]

Slow progression of HTN results in dilatation of LA. Large LAprovides ripe situation for looping sinus rhythm within itselfresulting in AF. The LV is increasingly dependent on atrialcontraction for adequate filling. Sudden onset of AF offsets thisfilling, leading not only to inadequate LV filling but also elevatedLA pressure which transmits to pulmonary vasculature. Fibroticarea can act as a substrate for ectopic rhythm generation whichresults in chronic intractable AF and lead to clot formation withthe risk of systemic embolization.

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Clinical flow chart for echocardiographic evaluation of hypertension Nair

Excessive LVH causes smaller LV cavity with low strokevolume. It also leads to disorganization of the LV contraction ofdifferent layers. This can be measured by strain imaging. ExcessiveLVH results in different areas achieving peak contractions atdifferent times. This mechanical dispersion can be measuredby strain imaging. Evidence is emerging that dispersion beyondstandard deviation can cause ventricular arrhythmias and suddencardiac death (SCD). Prediction of subsets of such patients likelyto develop ventricular fibrillation and SCD may be possible infuture by the use of strain imaging echo technology.[6]

Conclusion

According to the most recent guidelines, initiation andmonitoring of the response to the treatment of HTN arebased on clinical findings. Echocardiography is the second-lineapproach in evaluating selected patients. It provides valuableassessment of cardiovascular risk at clinical and subclinicallevels. Standard 2D and 3D echo techniques detect end-organdamage at clinical level. New techniques like strain imaging helpto diagnose dysfunction at subclinical level. Early detectionand treatment can prevent progression of hypertensive heartdisease.

 
References
  1. Clinical Implications and Treatment of Left VentricularHypertrophy in Hypertension. Available from: http://www.uptodate.com. [Last accessed on 2019 Jun 20].
  2. Lee JH, Park JH. Role of echocardiography in clinicalhypertension. Clin Hypertens 2015;21:9.
  3. Karabinos I, Grassos C, Kostaki P, Kranidis A. Echocardiographyin the evaluation of a hypertensive patient: An invaluable tool orsimply following the routine? Hellenic J Cardiol 2013;54:47-57.
  4. Parashar SK, Gupta R. Comprehensive 2D Echo and DopplerBook. Delhi: JROP Institute; 2018.
  5. Marwick TH, Gillebert TC, Aurigemma G, Chirinos J,Derumeaux G, Galderisi M, et al. Recommendations on the useof echocardiography in adult hypertension: A report from theEuropean association of cardiovascular imaging (EACVI) andthe American society of echocardiography (ASE). Eur Heart JCardiovasc Imaging 2015;16:577-605.
  6. Karol A. Role of Echcardiography in optimal management ofHypertensin Manual of Hypertension-Hypertension society ofIndia. Ch. 20. New Delhi: Jaypee Brothers; 2016. p. 172-80.

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