Feeds:
Posts
Comments

Posts Tagged ‘lvh q waves’

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.

Read Full Post »