Midwall left ventricular systolic function in cardiac hypertrophy

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Midwall left ventricular systolic function in
cardiac hypertrophy

• J Mayet, B Wasan, B Ariff, N Chapman, M Shahi,
  NR Poulter, PS Sever, RA Foale, SAMcG
  Thom
• Peart-Rose Clinic and Department of Cardiology St
  Marys Hospital, Imperial College, London

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Is LV systolic function preserved in LVH?

• Discrepancy between experimental and human
  studies
• Former suggest myocardial function depressed
• Latter indicate it is preserved
• Experimental and human studies not strictly
  compatible
• Experimental studies measure myocardial or
  myofibril function
• Human studies have assessed whole heart function
  by utilising endocardial measurements

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Midwall LV shortening

• It is often assumed that the inner and outer
  parts of the LV wall thicken equally in systole
• Myocardial shortening in subendocardial is
  greater than subepicardial layers
• Therefore a theoretical mid-point in the LV wall
  shows relative migration toward the epicardium
  throughout contraction

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Epicardial migration of theoretical midwall fibre
during systole
...
...
Posterior wall
Theoretical midwall fibre
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Midwall LV shortening

• Anatomic reasons why assessing shortening at the
  midwall may be preferable
• At the midwall circumferentially orientated
  fibres predominate while at the epicardium and
  endocardium fibres are longitudinally orientated
• When circumferential wall stress is considered to
  assess stress-shortening relations then correct
  anatomic plane is being addressed

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What is the relationship between endocardial and
midwall shortening in normal subjects and those
with LVH?

• 38 previously untreated hypertensives with LVH
  compared with normotensive controls (healthy
  volunteers)
• No patient had significant co-morbidity
• Each underwent full two-dimensional
  echocardiographic examination

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How does regression of LVH effect midwall
shortening?

• 32 hypertensive subjects with LVH
• 24 previously untreated
• 8 uncontrolled on existing medication
• Echocardiography at baseline
• Treated with ramipril with addition of felodipine
  and bendrofluazide if required
• Echocardiography after BP control
• Echocardiography after a further 6 months of BP
  control

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Calculations from echocardiographic data

• RWT 2xPWTd / LVIDd
• FS 100 x (LVIDd - LVIDs) / LVIDd
• End-diast volume 7 x (LVIDd)3 / (2.4LVIDd)
• End-syst volume 7 x (LVIDs)3 / (2.4LVIDs)
• CO HR x SV HR x (EDV- EDV)
• EF 100 x (EDV - ESV) / EDV
• cESS
• SBPx1/2LVIDs2x1(1/2LVIDsPWTs)2/(1/2LVIDs1/2
  PWTs)2 / (1/2LVIDsPWTs)2-1/2LVIDs2

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Calculations from echocardiographic data

• In order to calculate fractional shortening at
  the midwall, the position of a theoretical
  midwall fibre in systole needs to be known
• This can be calculated by using a cylindrical
  model of the LV with the assumption that volume
  remains constant through the cardiac
  cycle (1/2LVID1/2PWT)2 -
  (1/2LVID)2
• End-diastolic volume
  ___________________________________________
  (1/2LVIDPWT)2 - (1/2LVID)2
• (1/2LVIDsa)2 -(1/2LVIDs)2
• End-systolic volume _________________________
  _________________
• (1/2LVIDPWT)2 - (1/2LVID)2
• Where a is the distance from the posterior wall
  endocardium of the theoretical midwall fibre at
  end-systole
• Because end-diastolic volume end-systolic
  volume a can be calculated
• From this Midwall FS () 100 x
  (LVIDPWT)-(LVIDs2a) / (LVIDPWT)

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Calculation of midwall fractional shortening
.
a
.
a
LVIDd
LVIDs
Midwall fractional shortening (LVIDd 2a) -
(LVIDs 2a) / (LVIDd 2a)
a
.
.
a
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Patient characteristics and echo results of
hypertensives with LVH and control subjects
plt0.01 versus controls
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Endocardial systolic function in patients with
LVH and controls
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Cardiac output and midwall LV systolic function
in patients with LVH and controls

p lt 0.01 versus control group
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Treatment study hypertensives with LVH
(males28, females4)
plt0.01 versus controls
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Changes in endocardial systolic function with
treatment and LVH regression
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Changes in cardiac output and midwall LV systolic
function with treatment and LVH regression

p lt 0.01 versus baseline
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What is the relationship between endocardial and
midwall shortening in normal subjects and those
with LVH?

• LVH group had a higher BP and a higher LVMI
• Endocardial measures of LV systolic function were
  similar between the 2 groups
• Midwall systolic function was significantly
  depressed in the LVH group

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How does regression of LVH effect midwall
shortening?

• Good BP control was achieved
• There was significant regression of LVH
• Endocardial fractional shortening was not
  significantly changed
• Midwall shortening improved with LVH regression

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Discussion

• In spite of similar endocardial systolic
  function, midwall systolic function is
  significantly depressed in subjects with LVH
  secondary to hypertension
• Midwall shortening is improved with regression of
  LVH using an ACE inhibitor and calcium antagonist
  based treatment regime
• A reduced midwall shortening has been found to be
  associated with a lower exercise performance
• Depressed midwall shortening has been shown to be
  an independent predictor of an adverse outcome in
  hypertensive subjects, particularly in those
  subjects with additional LVH