Posts Tagged ‘right coronary artery’

RCA is known for unusual variants.Here is a right main trunk which divides into two major branches, both taking a surprisingly similar course.Shall we refer it to as Dual RCA  or is it an early RV branch ? But how can both run posterior and parallel ?

PS: His LAD and LCX  were  normal.

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This is an  RCA of   a  patient who had chronic stable angina  , class 2  with moderate anti anginal medication.

What shall we do ?

  1. The RCA needs  multiple stenting
  2. Multiple plain balloon angioplasty
  3. CABG to PDA
  4. No intervention ?
  5. It depends upon status of LAD  and LCX

The correct response would be 5

Without knowing  the status LAD and LCX . . .  RCA should not be touched . Further,  the concept of tackling  the  coronary artery  by itself  is   fundamentally wrong !  We are supposed to tackle patient’s symptom ,   reduce future risk of  events and   not merely  their coronary artey !

His LAD and LCX was near normal. In the weekly  cath   meet   PCI to mid RCA  covering  the critical segment was  strongly debated but  lost a close race .

The final decision was to allow the patient to continue   intensified   medical management (Statin 80mg /Metoprolol 100mg ) . He is comfortable with that .

Medical management  in a tight  single vessel disease  can never be digested by  any   Interventional cardiologist  whatever   may be  the guidelines !

Final  message

Do not decide PCI on the basis of   how ugly a coronary artery looks , rather spend some time on true  symptomatology ,  optimise baseline therapy  and re assess risk profile

One learned dictum is ,  do not  meddle a RCA ,  however severe the lesion may be   if  LAD and LCX are fine.*

*This  rule is not applicable in ACS

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Myocardial infarction (STEMI)  occurs in two distinct arterial  territories .The anterior LAD circulation and postero- inferior RCA/LCX circulation.The incidence is equally shared.

There has been some  learned and unlearned perceptions about Inferior MI.

Inferior MI is less dangerous than anterior MI.  True or false ?

Answer: Essentially true in most situations.


Inferior wall of the heart (strictly speaking there is no walls for heart , only surfaces , which blends with adjacent areas)  inferior wall  is formed by diaphragmatic surface and posterior surface.Inferior MI can occur by either RCA or LCX obstruction.The outcome of inferior MI is determined by mainly by  the extent  of   LV myocardial   damage it inflicts.To  quantitate this  we need to know , how much of LV is supplied by RCA , or LCX or combination of both ? This depend on the coronary dominance .It is estimated , the bulk of the LV is supplied ( up to 75%  ) by LCA. This becomes further high in left dominant circulations . In fact , it is believed LV can never get involved in non dominant RCA occlusions. This has brought in a new terminology  called “Small inferior MI”.Inferior STEMI due to PDA  occlusion or in a co -dominant circulation is not yet studied

Apart from the above  anatomical considerations the following clinical observations  have  been made regarding inferior MI.

  • When thrombolysis was introduced , many studies  suggested the the ST elevation in inferior  leads toched the isolectric levels  in most situations even without thrombolysis.Technically, this implies spontaneous , successful thrombolysis are more common in RCA. Among the thrombolysed ,persistent ST elvation is a rare phenomenon.
  • The well known difference in the conduction defect between anterior and inferior MI  is an important contibutor for better outcome in the later.(AV blocks in inferior MI , are often transient, non progressive, supra hisian location rarely require permanent pacemakers)
  • During acute phase cardiogenic shock occurs in a minority (That too , only if RV shock is included )
  • Even in the follow up the ejection fraction in inferior MI is  almost always above  40%. In many EF is not affected at all.
  • Progressive adverse remodelling of LV is rare

When can Inferior MI be dangerous ?

Anatomical factors

Inspite of the  above  factors  inferior MI can not be taken lightly . Especially when it  extend into posterior, lateral , (Rarely anterior) segments.

While  posterior extension  is often  tolerated , lateral extension is very poorly tolerated .This is probably explained as  the extension involves the vital free wall of LV and the laplace forces could precipitate LVF. Free wall rupture is also common in this situation.

Posterior extension , predominantly involves the surface of RV which is less important hemodynamically. Of course incidence of MR  due to it’s effect on posterior mitral leaflet can be trouble some.

inferior MI ECG

High risk clinical catagories.

Out of hospital STEMI  are at  equal  risk irrespective of the territories involved  .This is because,  primary VF does not differentiate , whether  ischemia comes from RCA or LAD .

  1. In elderly , dibetics and co existing medical condtions  the the established  benign   character  of  inferior MI disappear, as  any  muscle loss  in LV has equally adverse outcome.
  2. Even though  inferior MIs are immune  to cardiogenic shock  , a equally worrisome  prolonged hypotension due to high vagal tone, bradycardia, plus or minus RVMI can create trouble. Fortunately , they respond better to  treatment. Except a few with extensive transmural RVMI outcome is good.
  3. Presence of  mechanical complications of  ventricular septal rupture , ischemic MR can bring  the mortality on par with large anterior MI.

How different is the clinical outcome of infero-posterior  MI with reference  to the  site of  coronary arterial  obstruction   ?

The sequence of  outcome  From  best to worse  : Non dominant RCA* → Dominant RCA but distal to RV branch → LCX dominant with large OMs

* It is believed   an  acute proximal  obstruction of a  non dominant RCA may not be mechanically significant, but can be electrically significant as it retains the risk of primary VF and SA nodal ischemia. The ECG changes  can be very minimal or  some times simple bradycardia is the only clue. One should be able to recognise this entity (Non dominant  RCA STEMI)  as the outcome is  excellent and these patients  would never require procedure like primary  PCI

** A inferior MI due to a dominant LCX and a large OMs have comparable outcome as that of extensive anterior MI. The ECG will reveal ST elevation in both inferior and lateral leads.

***In patients with prior CAD  and collateral dependent  multivessel disease  the  inferior anterior sub classification does not make much sense as  entire coronary circulation can be mutually interdependent.

Final message

Inferior STEMI  generally lacks the vigor  to cause extensive damage to myocardium in most situations .Further they respond better to treatment. Risk stratification of STEMI based on the location of MI has not been popular among mainstream cardiologists. This issue needs some introspection as  the costly and complex treatment modalities like primary PCI  is unwarranted in most of the low risk inferior MIs.

Related posts in my blog:

1.Why thrombolysis is more effective in RCA?

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                                                      Coronary arterial circulation is the life line for  the human heart  and it’s survival.Typically it is supplied by two coronary arteries,  left and right coronary artery.Both, together carry about  250ml of blood every minute.( Approxinately  equal to a  cup of  coke !  ).These coronary arteries  generally divide in a predetermined  fashion , and have multiple branches . It is a  mystery , what  decides this  branching pattern

Is it like a our palmar crease  ? or the cerebral gyri ?

However , it does follow a certain rule,  one major coronary artery  will follow the  four  important grooves of heart. In the left side ,  left main coronary artery (LM) originates in the left coronary sinus (Size varying between 1mm -20mm)  and usually bifurcates into LAD and LCX. The left anterior descending artery (LAD) runs in anterior interventricular  groove while ,  the right atrio ventriculo groove carries the right coronary artery(RCA) .Left  circumflex artery (LCX) traverses the  left atrio ventricular groove.The most inconstant branch is the posterior descending artery (PDA) which runs in the posterior interventricular  groove.PDA  can arise from either RCA, LCX or both or even from LAD.

The major branches of LAD are called diagonal and septal  while the branches of LCX are called obtuse marginal(OM).There can be two to three diagonal and OMs. 

What is ramus intermedius coronary artery ? What is the incidence of Ramus ?

The left main coronary artery  instead of bifurcating into two ,  it trifurcates into three vessels.(LAD, LCX, Ramus)

The real incidence could vary betweenn (10% to 30%) depending upon the series.


What course it takes ?

It generally goes in the angle between the LAD and the LCX.It may either behave like a large OM or a diagonal branch.It supplies the lateral free wall of the LV many times.The peculiarity of this vessel is it does not run in a anatomical groove .It simply slides over the free surface of LV.Rarely, a  very abnormal course of ramus,  criss cross the aorta and pulmonary artery .

How common is atherosclerosis within  Ramus ?

We don’t know yet. But it is very likely since it is an early branch from left main, it  might  have a  predilection for atherosclerosis  as like LAD or LCX ostium.In fact now we recognise more of  trifurcation lesions involving  three branches of left main .

What would be the ECG finding if a large ramus is the culpirit vessel during STEMI ?

This scenario could be rare.

ACS in ramus could  present as ST elevation in 1/Avl /V5,V6

  • Lateral MI
  • Apical MI
  • High lateral MI

But it is realised , whenever the ECG changes are not fitting with typical ASMI or a lateral MI one should suspect a ramus lesion

 What is the significance of ramus for an interventional cardiologist ?


                                                   PCI in ramus is a rare opportunity for a cardiologist .The issue here  is,  if ramus is involved  adjacent LAD and LCX is also likely to be involved .So it would logically be a multivessel , complex angioplasty.Isolated ramus lesion could be tackled easily.Another issue here could  be ,since this vessel is not within  any anatomical groove  stent deployment would have a poor  support and prone for mobilisation and migration .

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