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Posts Tagged ‘left ventricular hypertrophy’

We know LVH and SHT go together . Mind you , this is not an Intimate relationship.

Widespread utilisation  of echocardiography  has revealed  , definite  LVH occurs only in about 20% (A guess !) of  HT . (Do you know in the Famingham study the incidence of LVH  after 12 year follow up was a paltry 3 % .Will you agree with that ? Mind you , It was in 1969 when Echo was not there )

What determines LVH ?  The clear answer is elusive. It is easy to escape  from the issue by calling it  multi factorial !

Why don’t you try this question .

My guess would be ,  magnitude ( or  even duration of HT !)  is  less important than genetic predisposition  or  associated diabetes ,  renal involvement.Our analysis from  hypertension clinic reveals LVH is many fold common in secondary HT  when compared to primary HT !

I often used to provoke the students by saying if the LVH is gross in HT it can not be primary , 9/10 times  ! Invariably  we find some  other  association or reason for the HT !

Link to related topic in this site

Why-lvh-does-not-occur-in-all-patients-with-systemic-hypertension ?

How-diabetes-modifies-lvh-due-to-hypertension ?

incidence of lV left ventricular hypertrophy framingham study

Next  . . .

How does LVH regress with treatment ?

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Left ventricular hypertrophy (LVH) is the most common structural abnormality of the heart. Hypertension and LVH are close associates . Still ,not every one with HT develop LVH .  So,  there  obviously  is a missing link . Similarly , diabetes  in the company of   hypertension  love to  target the  heart muscle with more vigour .  The  incidence of LVH  can be near  100%  when DM  join hands with HT.

So, what is the secret ?

Sustained elevation of afterload  due to high BP   inflate the myocyte ,  result  in myocyte hypertrophy , which is more of a physiological response.  The diabetes mellitus  adds some spice to the hypertensive LVH.

Diabetes causes glycation of  myocyte cell membrane  proteins . This  opens the  flood gates  and  the  cell permeability barrier vanishes. Hence there is exudate collect in the  cardiac interstitium. This is  equivalent to diabetic microangiopathy seen in retina and  kidneys.

There is  well established link between diabetic LVH and microalbuminuria  , suggesting  a  protein  leak  equivalent  in   heart  (Myocardial proteinuria)  . The only difference  here  , is the  protein leaks into the interstitium   instead of  renal  tubules  .  As we know interstitial leak is a  powerful  stimulant for   fibrotic reaction and  new cell growth. Fibroblasts in combination with extracellular matrix  and macropahges form  a rigid  and timid myocardium . If the patient is also a dyslipidemic(  which is usually the case !)  the leaked LDL , TGL adds to the chaos .

Pathological  effects of  diabetic LVH

  • Increased LV mass
  • Early LA enlargement
  • Early diastolic dysfunction
  • Prevent regression of LVH  even after good BP control

Can  diabetes per se cause LVH without Hypertension ?

Yes .this is also possible , but it  is less recognised.Diabetic LVH  can be a part of generalised organomegaly seen.(Right from the days of fetus diabetes has a  tendency to increase solid  viscera  size –  Large babies in  diabetic mothers , diabetic kidneys rarely shrink !)

Other factors that are related to LVH in diabetes include

  • Female Gender
  • Insulin resistance
  • The lipid connection – Hypertriglyceridmia is linked to LVH

Can tight blood sugar control reverse diabetic LVH ?

We hope so . It may not happen in real life .it depends upon the extent of interstitial invasion of abnormally glycated proteins.

Can echocardiography identify diabetic LVH from hemodynamic LVH of SHT ?

The diabetic LVH is fundamentally different in that ,  the classical septal hypertrophy is uncommon, instead the overall LV mass is increased .This is logical,  as septal LVH is more often reflect hemodynamic stress .

Diabetes  infested myocardium   bright echoes arise  from within . This is due to reflection from  interstitial  proteins.

The newer modalities of echocardiography  like integrated back scattering  analysis can characterise  tissues.

Tissue doppler  myocardial spectral analysis  can identify LVH contributed by DM..

Final  message.

What we know about LVH ,  is far less than we do not know !  , especially when  a patient has a combination of DM and HT. The interaction between them  is so intimate ,  we fail to recognise individual contribution to the process. If only we decode this  mystery , we can intervene better in the  pathological progress of  LVH.

http://care.diabetesjournals.org/content/28/9/2255.full

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  • LVH is classically diagnosed with high qrs voltage either in limb or chest leads or both.
  • High voltage is a specific ECG  sign,   presence  of  which  would strongly suggest LVH  ,   absence of which  is not  useful to rule out true LVH.
  • LVH with   flattish  or  down sloping   ST segment ,  with or without  T inversion  , can be a sole presentation of LVH . This should not be taken as sign of ischemia.  Here is  patient  with such an  ECG

Mechanism for LVH without high voltage

  • Intrinsic muscle  electrophysiological  property – Arrangement of muscle fibre orientation  will determine the voltage .(Parallel vs perpendicular, disarray etc)
  • Pathological LVH with fibrotic process and interstitial hypertrophy may not  record high voltage.
  • Presence of  high voltage LVH  would indicate a dominant physiological muscle mass that lacks interstitial reaction.
  • Finally , technical cause like thick chest wall in obese can dampen the LVH voltage.

Read a related  topic in this blog

https://drsvenkatesan.wordpress.com/2010/07/21/why-lvh-generates-high-voltage-qrs-in-some-and-low-voltage-qrs-or-even-q-waves-in-others/

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LVH can be diagnosed with fair degree of  accuracy  by surface ECG . We have a set criteria .The Estes  scoring is  the most popular. Very rarely we have all  the classical features of LVH in a given ECG .

With the advent of echocardiography ECG diagnosis of LVH has become redundant . Still , it is essential to  build the  foundations  in cardiology  for the current generation cardiologists.

The following are the  magnified views from the above   ECG

High Voltage

High voltage QRS is a hall mark of LVH .It increases in both chest  and  limb leads .In chest leads , both R and S wave gets amplified , while in limb leads only the R wave  is taller . We have to sum up R  from lead  V 5 and S from V2  (Practically any deep S and tall R can be added . LVH is diagnosed  if  sum qrs voltage  is  >35 mm . Voltage criterias in limb leads do not require these  addition business . An  R wave amplitude > 11mm  in limb leads by itself  would indicate an LVH (In the absence of bundle blocks )

Pit falls in voltage  criteria

It is our belief    qRS voltage  would faithfully   reflect the   quantum of cardiac muscle mass ,  but in general  to equate qRS voltage  to myocardial  mass  is   a  huge error we make ! (Of course  It  may be true in  some cases  following MI )  .

The qRS  voltage is determined by   numerous  factors (Important ones are :  chest wall thickness , age , LV cavity size ,  amount of blood inside LV cavity,  heart rate , conduction delays  etc ) This is the reason a 10-year-old boy’s   ECG will  satisfy the criteria of LVH  by 100 % .Do not ever report a ECG without knowing the age of the patient .

At high heart rates R wave amplitude increases(Broddy effect) due to high conductance of blood

Chest lead always balances RV and LV forces .One can mask the other .So be ready for surprises when you find a perfectly normal ECH in bi-ventricular  hypertrophies ) A balancing act !

Mini summary : Never diagnose LVH with high voltage alone

Left axis deviation

The axis deviation is again non specific  . The LV mass shifts the mean axis to left (Beyond -15 degrees) .The axis shift would also be contributed by mild forms of LAFB . This  fascicle  which criss crosses the LVOT  easily gets injured to hemodynamic stress ( or rather insulted ) and  lose its function . So its job is  transferred to  the posterior fascicle  which  shoots  towards  anterior and superior and left , hence the  left axis deviation) .The LAFB is generally a benign defect unless it occurs in an acute fashion as a response to ischemia.

Mini summary : Never diagnose LVH on the basis of left axis alone

Left Atrial  abnormality

This need not be present in every one with LVH . It happens only  if  LVH  is associated with relaxation defect , when   it calls for  LA’s  assistance .(In other words , presence  of LAE in hypertensive  patients is  a  sure and simple way to confirm diastolic dysfunction ) . Similarly absence of  LAE (  with a   significant LVH )  is a good sign as the LV is able to tackle the hypertensive stress in solo fashion in all likely hood free from significant diastolic dysfunction.

Apart from LAE , note also the p wave encroaches good part of PR interval .

Mini summary : LAE can be very useful parameter to diagnose LVH . (Is it not ironical  to note   LAE is more reliable to diagnose LVH ! . This is because qrs morphology is unreliable as it influenced by many factors  while p wave  changes are  not subjected to such influence )

Secondary repolarization changes

We know ventricular depolarization and repolarization are interlinked phenomenon .Both  occur in  opposite directions still  , able to  record   ECG deflection  in same direction  (positive QRS/positive T)  . This is due to the fact  the epicardium and endocardium has  action potential with different velocities . At times of   LVH this epicardial  , endocardial heterogeneity in repolarization becomes void. (Note : This is a simplified statement of a complex repolarization process)

Because of this the repolarization is recorded opposite to that of depolarization .Hence we get all sorts of secondary ST /T changes. (The  term secondary is used to denote secondary to alteration  in depolarisation ).

Many times  all of the following  could   mean the same  in the bed side clinical parlance !

  • Secondary ST/T changes
  • Non specific ST/T ,
  • LV strain
  • LV systolic over load etc .

Note : Primary ST depression occurs in true ischemia without any alteration in LV Mass or conduction defect.

*** For advanced readers  only : Some of the ST depression that occur in ischemia could again be secondary changes. This  needs further reading.

Definitions

Echo is the gold standard for diagnosing LVH .There are two definitions .

  1. Based on septal thickness
  2. Based on LV mass*

LV mass > 200mg in men and 175mg in women is considered LVH . LVH based on LV mass is  ideal . But can be misleading in a dilated heart where the mass may be increased with a  relatively   thinned  out IVS .

Final message

There are numerous  ways to miss    LVH in ECG,  But the definite way  for not missing  is by echocardiogram !


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LVH is supposed to produce tall R waves . But , we know  often LVH is misdiagnosed as   myocardial infarction especially  anterior MI.  (With deep q waves*  in v1 to v3 and sometimes q in inferior leads as well)

Infarct tissue  is a  cluster of dead cells  , while  LVH is a bundle of live cells . How can the ECG produce similar changes  in both ?

One need to realise ,  ECG does not function  as  a tissue identifying  machine.  It’s job is to simply  tell which direction the current  is traveling with reference to the  recording electrode .

If it comes towards  the electrode ,  R  wave is recorded and  if it goes away Q is recorded.

In infarction it is obvious the dead cells  form a distinct electrically inert  window so that the  muscle  mass located in the opposite pole  (If viable ) will record  q waves.

In LVH  how the  direction of  current get reversed ?

We know,  cardiac muscle  is made  up of not only myocytes , it is enriched with, fibroblasts, interstitial cells, collagen and other extracellular matrix .These non contractile cells have little electrical energy to show off.  In physiological LVH there is  not much proliferation of interstitium . It simply  reflects hypertrophy of  individual contractile units. It robustly produce good quality electricity and the ECG inscribes a tall r waves

Causes of  physiological LVH include

  • Athletic heart
  • Many of the hypertensive patients
  • Early stages of Aortic stenosis
  • Any LVH due to increased loading conditions( In the initial stages )

Pathological LVH

Here  LVH  is predominately  due to  proliferation of fibroblasts  and interstitial cells  .This interferes with the alignment of sarcomeres of myocytes. When the  architecture of contractile units  are  altered ,  it finds difficult to generate good quality action potentials  . Since the ECG is the summation of action potentials  ,  it gets distorted  with local delay,   notch ,slur etc . Ultimately it many  cases q waves are inscribed .

Th  q waves ,  gets amplified by the fibrotic process which is  technically dead cells for the ECG machine at least !.

Note: Pathological LVH grows well with excellent nourishment from ACE gene dependent growth factors. In fact , who will develop pathological LVH  (and who will not  )  is  predetermined by our ancestral genes.  (Other wise called fate or destiny  !)

Conditions  causing pathological q waves

  • About 10% of  LVH due HT can manifest q waves
  • HOCM
  • Late stages of Aortic stenosis
  • Some cases of Diabetic HT combination
  • HT with CKD

* There is one more cause for q in LVH .This is technical .   As  the  heart rotates counterclockwise ,  septal activity instead of  recording a r wave  ,  merges  with the s wave mimicking q waves. In fact this could be very common cause for labeling LVH as MI.

Final message

Q waves are not sacred to diagnose MI.It can be generated  even by live myocytes  when it behaves like an  electrically dead ones.

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LVH is one of the commonest ECG abnormality . We know the hall mark  of LVH is increased QRS voltage .We also know , ECG is not a fool proof method to detect LVH .It has very good specificity , but little sensitivity , meaning that increase in  QRS voltage is  fairly accurate in predicting LVH  but absence of  which cannot exclude LVH.

Why Increased QRS voltage does not occur in many with LVH ?

Even though we think myocardial mass  is  the  sole determinant of QRS  voltage  , in reality  it   is determined by many other factors.

  • Distance between the ECG lead , and the myocardium is an important factor. In classical concentric LVH , the LV  cavity is not enlarged ,in fact it may shrink a little as the hypertrophy grow inwards and obliterate the LV cavity.(We do not know yet , how much of LVH grow out and how much  muscle grow in ! )
  • The blood volume within LV is a very good conductor of electricity.A good volumed LV may augment a QRS voltage.
  • This can be observed in some of the patients with DCM , where high voltage QRS  is recorded mimicking LVH.

But ,what really matters is the fine balance of blood volume and myocardial mass that determine the incidence and magnitude of LVH pattern in ECG.

QRS voltage as a tool to differentiate pathological from physiological  LVH

We know QRS current is generated from within the myocytes .If the myocytes  are  uniformly hypertrophy without altering the  basic mechanical and electrical architecture QRS complex will be amplified in a sm0oth manner and result in  classical high voltage  QRS  of LVH.

If the hypertrophy occurs in a disorganised fashion, where in myocardial fibres slips out of plane  with adjacent muscle bundles, the QRS  voltage may not increase and even be slurred or notched as we see in many cases of LVH with non specific intravascular conduction defects

The classical disarray of myocardial fibers that occur in HCM causes  pathological q waves.

* Other factors that determine LVH include bundle branch conduction delay or blocks which is not discussed here.(Ex: An incomplete LBBB can amplify the qrs without any LVH )

LVH with fibrosis

Fibrosis is not a standard feature of LVH. It occurs in few who are genetically predisposed , and  mediated by heightened sensitivity to circulating growth factors.

  • Fibrosis can have wide impact on the electrical as well as mechanical function of heart.
  • Fibrotic heart has a  potential to  blunt the  high voltage  QRS complex.
  • It  may even cause  pathological q waves .It predispose to ventricular arrhythmia
  • It prevents regression of LVH , even after the loading conditions corrected.

Other conditions that  attenuate LVH features in ECG

  • Diabetic hypertensive show less ECG voltage than isolated HT .
  • CKD patients often do not show ECG features of LVH inspite of LVH

Final message

Diagnosis  of  LVH by ECG is a  simple clinical exercise , but we realise now , the underlying mechanisms are too complex .

A simple question , ie  Why  every one  with LVH  do not increase  their  QRS voltage  ?  . . . exposes  our ignorance on the subject!

But one thing is clear, physiological LVH (Meaning LVH ,  purely due to loading conditions including SHT/Aortic stenosis)  more often result in high voltage , while  in true pathological LVH(infested with fibrosis ) the  increase in voltage is not consistent .

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Left ventricular  hypertrophy (LVH) is one of the most common  structural heart disease.Systemic hypertension, aortic valve disease are responsible for the bulk of the cases .Some  of the LVH occur due to cardiomyopathy (HCM/Non HCM variants).Athlete’s heart is a physiological response to exercise and  it  is largely a normal entity.

How many patients with SHT develop LVH ?

It is surprising to note , not every patient with SHT develop LVH .In fact estimates suggest only  about 30-40% of chronic  hypertensive individuals develop SHT .

What are the determinants of LVH in SHT ?

  • Magnitude of systolic pressure
  • Magnitude of diastolic pressure
  • Pulse pressure
  • Duration of SHT
  • Age
  • Gender
  • Body  weight/Obesity
  • Effect of treatment

While any of the above factors may operate in determining LVH

none of the above are important than this

“Genetic susceptibility ”

The myosin isoforms are determined by the genes .The re expression of   fetal isoforms in adults is responsible for LVH in many .This is determined by the genetic homogeneity

LVH  in  renal disease

Secondary hypertension due to renal dysfunction is a major determinant of LVH. This is espcially true if the pateints are dialysis dependent.The mechanism are not clear .

Diabetes and SHT :  LVH  friendly forces

When diabetes alone and SHT alone is less likely to result in LVH the combination of these two entities greatly increase the likely hood of LVH.DM induced microangitis amplifies the after load effect of HT and result in early LVH.Further this LVH is different from pure forms of hypertensive LVH  in that the interstitium goes for hypertrophy and in some cases neovascualrisation. In hypertensive LVH it is predominately myocyte hypertrophy  with little interstitial  proliferation. this has important therapeutic implication as any drug which reduce the blood pressure can regress pure myocytic hypertrophy, while in diabetic LVH  regression is difficult to achieve .

Lipid levels inversely related to LVH ?

There is no consistent relation between lipids and LVH .Occasional reports suggest a negative correlation.

Which LVH is associated with diastolic dysfunction ?

It is a well known fact , LVH has major effect on LV diastolic function.But it is also a fact only some forms of LVH develop this. Now it is clear only if the interstitial hypertrophy occur  diastolic dysfunction is manifested.  Even as the as the hypertrophied  myocyte  continue to  relax  the interstitium do not have molecular mechanisms to relax .Hence, as discussed earlier , diabetic hypertensive patient often  develop diastolic dysfunction .

Final message

LVH is not a simple expression of raised after load.It has major  non hemodynamic determinants which if identified , could have important therapeutic implication.

Coming soon . . .

Can  coronary artery  disease induce LVH in the absence of SHT or DM ?

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