Posts Tagged ‘incomplete lbbb’

A 60 year old man with chest discomfort and severe breathlessness  and  blood pressure of 160/110 was  wheeled into CCU. A diagnosis of  acute anterior  STEMI was made and he  was about to be  thrombolysed . Since  his blood pressure was high they were waiting for it to come down with IV  Nitrglycerin

I was called to see this  patient  .Here is his ECG .


Though   ECG  suggested anterior  STEMI  , I  was  fairly  convinced  it  was  in fact  LVH and  incomplete  LBBB.

I confirmed with the  patient  about the onset of symptoms . It was primarily  breathlessness and only a  vague discomfort .Meanwhile , the troponin came as positive and CPK MB    was  normal. The combined troponin  positivity  and ST elevation  almost confirmed the STEMI ,  and  the  urgency for  thrombolysis was  intensified . One resident suggested  an  emergency PCI.

My self ,  in spite of  being a cardiologist was isolated among the physician team .  I  had to  urgently  prove to them it is indeed  not STEMI !  I did a bed side echo and showed  the  physician colleagues   a vigorously contracting  hypertrophied  left ventricle  with a EF of 68 % . There  was  negligible wall motion defect  . . .  if at all any !

They were still far from convinced ?  They  were  sort of  amused .There is   ST elevation ,  there is  troponin  positivity. . . what else you want  . . . they seemed to ask  ?

I asked them  . . . How can an  acute  extensive anterior   MI contract so well ,  without a trace of   wall motion defect ?

It took me considerable time and effort  to  convince them  that the whole thing was not a STEMI.  Finally they agreed .It was  a simple LVH with secondary ST elevation  due to incomplete  LBBB .  Troponin elevation  simply  represent minor myocardial  injury associated  with hypertensive  LVF . This  patient was discharged within 24 hours  in perfectly stable  condition . Since he had mild elevation of creatinine and was  sent for  nephrology  work up.

Final message

LVH with secondary  ST elevation in V1-V4 is a common situation that mimics  acute STEMI . Cardiac failure can result in non ischemic troponin  release .  Acute medicine is  an unique art . Some times it demands all your senses to be on alert mode . Realise ,  in the above case ,   in spite of the   the classical   triad of  chest pain ,    ST elevation , troponin positivity  it  almost led to a wrong diagnosis of  acute myocardial Infarction .

After thought : What  if they had thrombolysed this patient or taken for a PCI ?

When  the clinical suspicion is high and  circumstantial evidence  point to an ACS   ,   this error can be  justified . After all ,  5 % of   famous ISIS  study population were not suffering from STEMI  but got thrombolysis !

* One real possibility in this ECG is  old AWMI with re-infarction  or a dyskinetic septum lifting the ST segment .But both were excluded by the rapid bed side echo.




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LBBB is probably the most important  conduction defect of the heart .When we say LBBB , we visualize a  strikingly  wide bizarre qrs complex .

Left bundle even though is considered  a discrete structure , the fascicles  make it a diffusely spread structure. Many varieties of LBBB with various degrees of involvement occur.

Talking about the basics of  LBBB  electrophysiology  is out of place for the current generation cardiologists,  who  have little spare time as  they sweat it out inside the cathlabs.

In early 1960s and 70s great articles came from pioneers regarding these defects. If we want get a good insight  read  this  articles from  Sodi palleres .Who  says LBBB is a dynamic process, where it can occur from mild functional  delay to a total block .

The conduction  properties of left bundle is very much influenced by heart rate.

Law of statistics would  suggest  for every complete LBBB  at least three to 4 times incidence of incomplete  LBBB

Then . . .

Why we are not diagnosing ILBBB often ?

  • We miss it
  • Mistake it with LVH
  • We know it  is there , but we do not  want  to diagnose it .

How to diagnose ILBBB?

See  Sodi palleres criteria*

What is the relationship between qrs width and completeness of LBBB ?

Surprisingly and contrary to the belief , the width of the qrs has no linear correlation between severity of LBBB. In fact incomplete  LBBB can occur with even 150ms qrs !

Then ,  what  exactly determine the completeness of LBBB ?

What  matters is , whether the down coming impulse gets blocked  and split in the  left side of the IVS or not ? This causes the  the septal vector to  change  it’s direction ( ie  right to left instead of the normal left to right) It  removes the initial small r wave in v1  and q in v6  in complete LBBB. In  incomplete LBBB these  r and q are  often retained .

What is the differential diagnosis of ILBBB ?

Type B WPW may mimic LBBB and vice versa.

LV hypertrophy .

Differences : See table in  the Barold’s article  linked above .

Unanswered questions

  1. How common is ILBBB in STEMI ?
  2. How often ILBBB progress to LBBB ?
  3. ILBBB in dilated cardiomyopathy : Is desynchrony an issue ? (Normal QRS CHF !)
  4. Is functional  rate dependent  LBBB in cornary care units  same as transient  ischemic LBBB ?
  5. Intermittent LBBB and Incomplete LBBB  aren’t they  synonymous ?

Final message

ILBBB is not that uncommon as one would  tend to perceive.


My humble tributes to  Barold, Sodi -palleres , and Leo  Schamroth . Probably  one of the best  article on ILBBB is linked below. Reviewed    in 1963 !  Not much data has been added  in the next 47 years as on 2010

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