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Posts Tagged ‘RVMI’

How to manage refractory RV shock with infero-posterior MI ?

Posted in Cardiology -Interventional -PCI, cardiology -Therapeutics, Uncategorized, tagged , on January 27, 2013| 1 Comment »

Right ventricular infarction (RVMI ) is a  common  cardiac emergency in coronary care units. It can be termed as a mechanical complication of infero-posterior STEMI .However ,  around 10 % of anterior  MI do develop this complication . Onset of refractory hypo-tension in spite of correcting hypovolemia  suggests  RVMI.RVMI generally comes under class 3  (Cidar Siani /Diamond -Forester classification of STEMI )  , ie   silent lung with systemic hypotension.       (RV shock requires an unique definition , as it can not be included in traditional  definition of cardiogenic shock as the PCWP is likely to be normal.

How to manage a full blown RVMI  who is not showing  signs of improvement ?

Following is an extract  from our coronary care unit experience

(do not ask for evidence for everything !)

  • Consider immediate angiogram  to know the  anatomy of the problem .Try opening the RCA which is most  likely to be  the culprit (Any associated critical  LCX /LAD lesion  must be attended too ! )If  the duration of MI is beyond 36 hours  culprit lesion may be  left untouched or at least not our primary target !
  • Inotropic support (Doubtamine continuous infusion is preferred .Milrinone  for the rich !)
  • There is no specific RV assist devices available.(LV  assist device has no role in RV )
  • Restrict fluid (Opposite  to RVMI guidelines) There have been instances of  overzealous fluid therapy resulting intra-cardiac  hypervolemia. IVS encroaching LV worsening the cardiac index .
  • Pacing is  definitely required in severe bradycardia or CHB .  Dual chamber pacing is the  ideal  choice to maintain AV synchrony as we desperately need  the  atrial booster pumb  for a failing RV . (Please realise , VVI  pacemakers ,  can still save lives as it takes care of extreme bradycardias  effectively )
  • PCWP in the setting  of RVMI is an  unreliable parameter of true cardiac function.(In almost 90 % of RVMi some degree of LVMI is present ) . In RVMI  PCWP is determined by a  delicate balance between LVEDP and the  onward stroke volume from a failing RV .) The alter tend to bring the PCWP down former would keep it high . Which component is  operating at a given point is a  wild guess  . The situation get quiet complex in the setting of multiple vaso-active drugs , pacemaker , ventilator
  • Balloon Atrial septostomy  /dilatation might help ( Hypoxia may worsen as elevated RA mean pressure may shunt right to left  however cardiac out put might improve)
  • Pericardiotomy  or simple splitting  of pericardial  layers has been tried   (Improves RV restriction effect)
  • If the patient is on ventilator keep the PEEP well below the standard recommendations (RV will struggle more ! )
  • Pacing catheters  can irritate the RVMI in their  raw zone and trigger recurrent ventricular arrhythmia .( Often  labelled wrongly  as Ischemic electrical storm !)
  • Call  Nephrologist  consult  if  renal function  deteriorates . Peritoneal  dialysis is preferred  .  It  is worthy to know , deaths have occurred on hemo dialysis  table.

Final message

RV shock  carries a dismal  outcome , almost  reaching  as that of an LV cardiogenic shock. Ironically ,the most important prognosticator  in RVMI  is the quantum of LV involvement !

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In acute coronary syndrome , can you legally thrombolyse in the absence of ST elevation !

Posted in cardiology- coronary care, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , on September 9, 2010| Leave a Comment »

Thrombolysis is specifically indicated when there is  ST elevation in ECG. ST elevation is a surrogate marker for  total coronary occlusion. It occurs due to current of injury flowing   towards* the lead  facing the  infarct territory . There is only one situation where you can safely and effectively administer thrombolysis in the presence of ST depression ie

Note : There is no accepted terminology  to label a MI as  ST depression MI . Here it is used to emphasise ST elevation is not the only indication for thrombolysis .In posterior MI there is infact ST elevation but it is failed to pick up by standard 12 lead ECG.

NSTEMI is a different entity altogether and  thromolysis is never indicated.

Isolated ST depression in V1 V2 V3 .It almost always indicate isolated posterior STEMI. This can be confirmed by posterior chest ECG leads V7-V10 .

*One will be surprised, to know  the mechanism of ST elevation in STEMI is still not fully elucidated .Technically speaking the net movement of current is away from electrode as  there is only a baseline  diastolic shift  which  gets neutralised in systole  mimicking an ST elevation .(Electro-optical illusion !)

How sensitive is these leads to detect isolated posterior STEMI  ?

Fairly sensitive. Both scapula and  para spinal muscles can be a  significant electrical  barrier that can prevent ST elevation from inscribed .In case of doubtful ST elevation in posterior leads , mit is always better to rely on the clinical presentation.Acute chest pain , consistent with ACS and a new onset ST depression >2mm V1 to v3 is a definite indication for thrombolysis .

Link between posterior MI and RV MI ?

They are closely linked entities .In fact posterior surface of heart is contributed significantly by RV.

What is the angiographic correlation of  isolated ST depression in V1 to V3 ?

It almost always localise the lesion to left circumflex artery . If it is dominant , it can involve lateral and RV territories.

Is isolated posterior MI  less dangerous ?

May be yes , but only after the patient reaches the hospital as electrical risk is same in every STEMI .

The area of infarct  is less , LV failure is less common. While conduction disorders and ischemic mitral regurgitation   can occur  significantly.

Also read ,  Why thrombolysis is contraindicated in UA/NSTEMI ? in this blog

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Acute myocardial infarction of LVOT : An unrecognised cause for refractory hypotension

Posted in Cardiology - Clinical, Cardiology -Interventional -PCI, cardiology -Therapeutics, Cardiology -unresolved questions, tagged , , , , , , , , on February 6, 2010| Leave a Comment »

Hypotension is one of the dreaded complication of acute STEMI.

  • It can be due to either a  mechanical complication or hypovolemia.
  • The hypotension in inferoposterior MI is  often related to enhanced vagal tone and easily correctable with atropine  and fluid  administration.
  • RVMI is the classical example of hypotension that may improve with fluid resuscitation
  • Hypotension,  if  not reversible within 12  hours  ,  is more likely to  represent a more sinister mechanism like pump failure, MR or ventricular  septal tear etc .

A new mechanism for persistent  hypotension is increasingly recognised.

This is due to the

1.Loss of LVOT dynamic activity.

2.Excessive  dynamism of LVOT.

LVOT contractile and ejectile falure

Even though LV  outflow tract  contain  less  contractile myocytes  , it has an important mechanical  job to do. We know , it’s  primary job is that of a  conduit  but  it also  has to  eject the blood into aorta with sufficient force.  In fact, it is thought much of the acceleration of blood velocity occur in LVOT . So, LVOT  plays a key role in maintaining the cardiac index.  An excessively dynamic LVOT will impede the forward blood flow as in HCOM.  Similarly  less dynamic contraction  of LVOT  results in  low velocity propulsion , that interferes with   proper delivery of blood from LV cavity into the aorta .

These factors get amplified in  acute MI , as it is a compromised situation with fluctuating HR and contractility. So a properly functioning  LVOT conduit is  absolutely mandatory.

STEMI due to a proximal LAD obstruction   located can involve the septal .If the first septal branch  happens to be a major one,  there will be  definite impact on the LVOT function.

Excessive dynamism  , LVOT   desynchrony  LVOT collapse .

LVOT has a medial border formed  by IVS , an  anterior surface and  a posterior surface .The lateral border is relatively boundary less , except it is guarded by  the anterior mitral leaflet.

But one should recall , the AML comes towards the LVOT only in diastole . When it comes in systole it becomes a pathological event  called  SAM  (Systolic anterior motion )

The LVOT wall desynchrony can occur in both anterior and posterior MI.In a mulivessel CAD  this can happen when there is disproportionate inferior to anterior wall motion defect.

Management.

  • There is no specific management strategies aimed at restoring LVOT function.
  • Emergency revascularisation will attenuate the mechanical dysfunction
  • Dosage of powerful inotropic agents should be moderated in dynamic LVOT obstruction.
  • Spontaneous recovery  may occur in few

http://circ.ahajournals.org/cgi/reprint/116/5/e110.pdf

Haley et all Mayoclinciproceedings 1999

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Why we look lead V1 to diagnose RVH but look at V4R , to diagnose RV infarction ?

Posted in Cardiology - Clinical, tagged , , , , , , , , on July 2, 2009| 1 Comment »

The right ventricle  is a unique  chamber of the heart . It is the anterior most chamber and  triangular in shape.  Even though  the walls of RV are  not  clearly demarcated ,   it does  have  anterior ,  posterior, and lateral free surfaces   . Anatomically it has a inflow  body, apex and outflow portions . The apex of right ventricle , blends with the lower IVS at an acute angle.

How does RVH occur anatomically ?

The anatomy of RV is such that  it does not allow  it  a concentric  RVH ( like LVH ) . In fact , there is a  disproportionate free wall , anterior  wall   hypertrophy  many  situations  like  PHT/Pulmonary stenosis. The  infero posterior aspect of RV rarely show hypertrophy.

Since RV is the anterior most chamber, located just beneath the left border of sternum   RVH brings the RV  further closer to chest wall .This makes the V1 lead to show  tall R in V1.

What happens in RVMI ?

Unfortunately, when we  refer to RVMI , we generally do not make any efforts to locate or estimate it’s  size.  Since RV has , anterior , lateral and posterior surface  , the site  and  the  extent of the  mI will have a major impact  on the  ECG  features .

Most often  the RVMI occur as a  part of infero posterior MI  .Hence ,  it is uncommon for the anterior surface of RV to get involved.  But ,  it can be involved if  RCA gives of a   large RV branch  that reach the anterior surface of RV.

Anterior RVMI can occur as a part  of LAD MI  , if a large conal branch cross the RV surface.

What prevents the lead V1 from showing the  ST elevation of RVMI ?

  • Most of the RVMI do not involve the anterior surface of the RV so , less chances for ST elevation
  • Further , if a true posterior wall  MI  occur as a part of  RVMI (Which is often the case !)  V1 can never  show ST elevation  as the  posterior MI  tend to have a ST depressing effect in the V1, V2 leads.
  • Extensive IWMI , can have reciprocal ST depression in V1-V2.This again , prevents V1 lead to show the ST elevation

So many times , even though V1 lead is just sitting over the chamber RV it fails  to  pick  the  ST elevation forces of RVMI

Advantage of V4 R ?

V4R records remote RV forces , as these  signals are not contaminated by the inferio posterior ST forces. Hence  a  1mm ST elevation in right sided chest leads have good sensitivity  and specificity to diagnose RVMI .

When can V1 show ST elevation in RVMI ?

If the RV anterior wall is predominantly involved (Ie Anterior RVMI ) ST elevation can occur in V 1 like a anteroseptal MI.

rvmi ecg

Rarely a q RBB can occur in V1 in isolated RVMI.

Final message

V1 lead , though anatomically proximal to RV has less value in diagnosing RVMI since this lead picks up  Infero posterior  negative ST forces  and  the anterior  forces of RVMI get neutralised . So relying on lead V1 to diagnose RVMI is not adviced , except when  the anterior surface of RV is predominatly  involved.

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