Differential cyanosis classically occurs in PDA with reversal of shunt when raised PA pressures /PVR is able to supersede the systemic Aortic pressure and drive the blood from LPA to descending Aorta bringing down the lower limb saturation.

Of course,  this can be undone by the presence of any other intra-cardiac shunts or aberrant left subclavian that arising from the desaturated descending aorta.

Other causes of reversed differential cyanosis 

Where the upper body is cyanosed (desaturated) and the lower half is not. There is a conventional list of conditions.

  1. Transposition of the great arteries (TGA) with patent ductus arteriosis (PDA) and elevated pulmonary vascular resistance
  2. TGA with PDA and pre-ductal aortic interruption or coarctation
  3. Supracardiac TAPVC* + PDA
  4. Anomalous right subclavian artery connected to hypertensive ductus through RPA

(*This occurs due to streaming effect ) Highly saturated superior vena cava (SVC) blood into the right ventricle, reach MPA / through a PDA, and to the descending aorta, with streaming of more desaturated blood from the inferior vena cava (IVC) into the LA through PFO (Ref Yap S H Pediatr Cardiol. 2009 )

Now let us add one more cause for  reversed differential cyanosis in the Modern Era

It is seen with ECMO in VA connection (Often reported in babies ) . The Aorta has high oxygen content entering from the femoral cannula going up into the Aortic arch., while deoxygenated blood from LV (because of failing lungs) reach antegradely to the Aorta. Ideally, the ECMO is expected to supply the entire aortic arch and hence oxygenation is uniform all over the body. It rarely happens as some amount of flow will come from LV unless its in asystole. However, If the severely dysfunctional heart tends to recover & lung oxygenation is very poor as well, the LV stroke volume competes with highly oxygenated blood coming from below ( femoral inflow ) into the Aorta , creating a watershed zone . This makes the deoxygenated blood perfusing upper half of the body and hyper oxygen saturation lower half. This is been referred to as North-south syndrome or (Harlequin syndrome the famous Italian comical character)

How to manage North-South syndrome?

  • Try to Improve the oxygen perfusion with high-frequency ventilation(This is logical first step , to improve the native lung function)
  • ECMO flow rate may be increased and overdrive the LV ejection .(This can be counter-productive as we are hitting a recovering ventricle)
  • Converting to VV ECMO if the hemodynamics allows. This is possible as North-south syndrome is a sign of recovering cardia function VV ECMO will convert it into a primary lung support


ECMO review article

LV dysfunction is one of the most commonly used terminology by cardiac professionals.It can be systolic, diastolic or global, regional etc. But, before dysfunction sets in, the heart fights. The Left ventricle can behave in many different ways when confronted with stress. It increases the force of contraction, elevates it’s Intra cavitary filling pressure and still accomplishes its task of pumping adequately. Further, It can build fresh muscle (LVH). It can double up with more heartbeats. (All these factors are referred to as cardiac reserve mechanisms)

These reserve mechanisms can be activated in the short or long term. In the long term, autonomic activation with neuroendocrine factors joins the compensation process.  These will work for some time till the circulatory system settles down to new homeostasis. However, they become counterproductive and becomes decompensated, ultimately heart failure sets in(Unless Intervened)


Is LV dilatation a mechanism of cardiac reserve ?

No one calls LV dilatation as a reserve or compensatory mechanism. (I wonder, why not ?) I think like RV ,  LV too has some potential to reversibly dilate . The quantum of which we are unable to estimate.This happens usually in response to chronic  volume stress* like regurgitant valves or high output states. Though cardiomegaly and a huge heart convey a sinister outcome, many hearts shrink if the primary issue is corrected.(Typically in Anemia, Beri Berri. We also know LV may transiently dilate in response to some toxic /pregnancy-related cardiomyopathy.

* Mind you LV poorly tolerates acute volume stress as in Acute AR/MR

The critical gap in our understanding is about this question.

When does LV dilate physiologically and when pathological persistent LV dilation sets in (The absolute state of irreversibly lost cardiac elasticity.) We also know dilated LV will consume more oxygen due to enhanced wall stress (Laplace law) and hence its possible LV dilatation begets further dilatation. Optimal timing of mitral and aortic valve replacement in patients with AR and MR directly depend on this knowledge.

Final message

We need clarity in the following queries

  • Is LV dilatation (with normal EF ) a sign of LV dysfunction?
  • If so at what level of dilatation?
  • Since LV dilatation  occurs in diastole can we fit this entity “Isolated LV dilatation” in the already confused spectrum of diastolic dysfunction?

Let us wait for the knowledge to evolve. Young cardiologists could take up this area for research.

I asked some of my experienced colleagues, how much time they inflate the balloon to deliver a stent? Most answers were spontaneous and unanimous “It’s hardly 10 seconds,  few said maybe up to 15s.

Can prolonged balloon inflation time reduce the need for post dilatation and prevent mal-apposition?

We know high-pressure Inflation( up to 20 atmospheres ) was a big revelation in the science of PTCA more than two decades ago. (Antonio Colombo JACC 1995  ) He proposed and proved high-pressure inflation eliminated the need for routine anticoagulation following stenting as approximation was better. He also pioneered the concept of dual antiplatelet therapy (DAPT) in the PCI arena.

Similarly, prolonged balloon Inflation  (30 to 60sec) could be another trendsetting tip to prevent malposition. It delivers more sustained pressure. Its believed the imparted centrifugal force and the inbuilt radial forces add up to the stent vessel wall Interface and prevent mal-apposition.

Is there a downside to high-pressure Inflation?

There must be few.  Potential new Ischemic events and arrhythmia. In calcium laden plaques( spur) risk of perforation may be enhanced.

Final message 

I don’t know why this concept never took off. Many of us still fear to inflate the stent balloon no longer than 10 to 20 seconds? Adhoc post dilatation with short NC balloon appears mandatory in areas of mal-apposition. Meanwhile, we also understand sustained (30-60s) high-pressure initial inflation could deliver the stent in a more synchronized and smooth fashion with a perfect metal/vessel wall interface. Further , prolonged balloon inflation times could make a routine (By the way who does routine ?)  IVUS/OCT redundant.

What do the experts say?  What does science say?  There is one meta-analysis that clearly says the advantage of long inflation time. This issue becomes much more relevant as it could avoid post dilatation which all of us know can be tricky. In fact, every balloon dilatation should be technically counted as another PTCA procedure and adds up to net total risk.


1.M. Saad, M. Bavineni, B. F. Uretsky, and S. Vallurupalli, “Improved stent expansion with prolonged compared with short balloon inflation: a meta-analysis,” Catheterization and Cardiovascular Interventions, vol. 92, pp. 873–880, 2018. View at Google Scholar 


Assessment of LV diastolic function primarily depends on the Doppler flow profile across the mitral valve and also to be noted are the 2D features of LA and LV for associated abnormality like LVH, LAE etc.

Why diastolic dysfunction assessment difficult in AF ?

Since most diastolic doppler mitral inflow parameters involve analysis of atrial contraction A wave, atrial fibrillation makes it difficult to assess diastolic dysfunction. Since we have only early diastolic velocity to assess, the changes confined to this E velocity is of paramount importance. This E velocity again is subjected to cycle length dependent alteration in both its acceleration and deceleration time , making things still more complex.

However, the following features help diagnose diastolic dysfunction in AF

  1. Lack of significant  E velocity variation (<20%)  Inspite of significant RR interval change.(This implies mean LAP is kept high irrespective of cycle length suggesting elevated baseline LAP)
  2. E deceleration time (<140ms) (In long cycle)
  3. Propagation velocity in color M Mode(Vp)  <45cm/sec might help (RR interval dependent, measure in the long cycle)
  4. E/e” in a single beat by dual doppler probe (Ref 1)  > 10 indicate diastolic dysfunction that correlate with PCWP> 15mmhg (Ref 1)
  5. Finally (and curiously ) presence of AF by itself may imply significant LV diastolic dysfunction. It could be due to an increase in atrial strain and afterload of LA (ie pre A-LVEDP) (Of course, It should be in the absence of mitral valve disease)
  6. LA dimension in AF*

*LA dimension is a very good sign of chronic elevation of LAP and diastolic dysfunction in the absence of mitral valve disease. However, AF can dilate the LA making it a less useful parameter. But, it should be noted in AF both RA and LA dilate together.So,  a disproportionate LA>RA (or if RA is normal size ) could still be a marker of baseline LV diastolic dysfunction.



  1. Kusunose K.Yamada H.,  Nishio S.et al.  Clinical utility of single-beat E/e′ obtained by simultaneous recording of flow and tissue Doppler velocities in atrial fibrillation with preserved systolic functionJ Am Coll Cardiol Img 2009 2:11471156


FFR is the ultimate hemodynamic test that measures the physiological Impact of lesions. Just pass a manometer tipped wire across the lesion and note the pressure drop (with or without Adenosine) All you have to remember is two cut off values  .8 for FFR and .9 for IFR. Abracadabra . . . yes you got the answer , whether to proceed with PCI or not? It’s as simple as that. We are no longer blind to physiology to which many coronary purists often criticize us.

ffr ifr fame study

Coronary physiology simplified

Now , answer this question.

Is FFR heart rate dependent? If yes, how significant it is?

This simple question on coronary physiology caused the maximum distress  to  a large expert cardiologist group

Some of the answers

  1. No, it doesn’t.
  2. I think it may be affected.
  3. Yes for sure, but it’s not significant
  4. Yes, it’s an important limitation

My Answer

It has to be yes, right, however minimal it may be. My interpretation of truth in FFR is, it can have a massive influence* . (*Unless you are sure (we can never be ) about achieving maximum hyperemia or this hyperemia is the same as physiological exercise.) In fact, the whole concept of FFR lies in the fact that it should induce enough HR raise that should be used as a surrogate marker for maximum hyperemia. Ideally, like stress testing, we need to test FFR at maximum heart rate and minimal heart rate. The difference could be documented as FFR max-min. This will throw new light into the physiology of microcirculation.

Should we need to create a heart rate corrected FFR?

Yes , I think we need to do it or else should report at what HR we are reporting the FFR. If FFR falls at a high heart rate and maintains at low it implies a significant lesion. So don’t get fooled with FFR of .9 measured at an inadequate heart rate.

IFR to replace FFR : On what basis?

Meanwhile, new generation coronary flow quantification tool IFR jettisoned Adenosine and simply measure diastolic instantaneous flow at resting state. This makes a mockery of coronary physiology, without a true debate about heart rate dependence of trans-lesional flow.

Impact on clinical practice

Even as we struggle to answer the fundamental question of the influence of Heart rate on FFR, many landmark studies had been done. They have ratified FFR as the most physiological modality to assess coronary lesion. Important guidelines have been written based on these studies. No one will ever know, the true impact on the current cardiology care,  had we included heart rate adequacy /correction as an essential criteria in those FAMEd studies we hype about.


All is well with FFR.It has been tested with various heart rates.

FFR at peak hyperemia means there is no further HR rate induced potential microvascular reserve. So a properly administered optimal Adenosine augmented FFR should not bother the HR variability. (But its only theory)

If FFR is ok . . . IFR should not be ok is it not?, For the simple reason, there is no hyperemia in IFR , what is the use of knowing resting flow reserve (RFR)



Postamble with a slice of History 

FFR is as old as the concept of PTCA. In fact, the original balloons used by the great Gruentzig’s * had a central port for pressure recording through which he measured both proximal and distal pressure curves to guess the significance of obstruction. After each inflation, he checked  whether both curves are drawn together which he speculated to indicate a successful procedure physiologically.

*What a stunning scientific mind the father of Interventional cardiology was blessed with, still inadequate for the Nobel committee to get convinced.

Rules of the PCI game 

  • Mind the physiology. It is the new norm in selecting the lesions for stenting.
  • Now, If physiology is ok, you have to mind the Anatomy and vice versa.
  • If Anatomical (severity of block )is ok, then, you have to mind the morphology and vulnerability.
  • Finally. and most importantly mind the patient’s symptoms and clinical scenario.

So what should we do in a case of 70 % LAD with  .9 FFR ? (Still shabby looking, eccentric plaque, looks vulnerable  with a thin cap on OCT)

  1. I will stent, no doubt.
  2. I shall wait, and treat with Intensive optimal medical management (OMT).High dose statins will surely seal the cap.
  3. I will defer and watch.
  4. I will teach the patient and their family the basics of coronary hemodynamics and accept their decision.
  5. I simply leave the LAD for God to heal.

Which is correct?

All can be fair depending upon the clinical scenario.

In the ACS setting, one can’t afford to ignore these lessons.

Many would argue even in CCS setting it need to be tackled with PCI.

But isn’t also a fact, (maybe, we have been taught wrong as well ) non-flow-limiting lesions are more at risk in terms of ACS risk.

Hmm . . . then why we Insist to celebrate the concept of FFR  and its magic cut off of .75?

Do we practice coronary care at its height of confusing times ? or Am I make it appear so? 

Watch this, (https://rutherfordmedicine.com/videos )It might help you to get a better answer. Its called FORZA study. freshly delivered at TCT 2019, San Francisco.It compares FFR vs OCT guided PCI



The term Ischemic cardiomyopathy(ICM) was originally coined by Dr. Burch from Tulane University, New Orleans, USA in 1970. For many decades there was skepticism regarding the existence of such entity. WHO classification over the years never included this term. ESC working group of 2008 (Elliott P, European Heart 29(2):270–276) decided not to include CAD as a cause for cardiomyopathy. Even the current MOGES system doesn’t invoke CAD as a cause for cardiomyopathy. But, I am sure, most of practicing cardiologists would agree, there is a need for such an entity.

Why there is much reluctance to diagnose Ischemic cardiomyopathy as a distinct entity?

It is because of the basic principle, that cardiomyopathy should be a primary disease of cardiac muscle. (or at least secondary ).The presumption is, Ischemia per se doesn’t lead to muscle disease as such. It is just nutrition deprival.

Does this justify?

No, not at all. When a cardiac muscle is chronically deprived of nutrients it goes for necrosis, dilatation, scarring and dilatation, and progressive LV dysfunction. At some stage, it becomes true muscle disease or its equivalent (Secondary cardiomyopathy).In fact, adverse remodeling, Infarct expansion, extension lead to myocyte disarray, slippage and apoptosis, and cellular and interstitial fibrosis. All these changes are similar to Idiopathic (Postmyocarditis)cardiomyopathy.

What happens in the real world?

Even though there was some hesitation to diagnose ICM in the past, gradually the term shrugged of its taboo in academic circles. In heart failure clinics the only question seems to matter for everyone is, Is it Ischemic or non-ischemic DCM? Surgeons and EP guys also actively pursued the term Ischemic cardiomyopathy while they are selecting patients for CABG or CRT/ICD etc.

Further, in the research world involving community-based heart failure cohort, they required a basic distinction between the group of Ischemic from Non-Ischemic cardiac failures.

DUKE university definition (By Felker et al)

I think DUKE ended the controversy in the Nomenclature of Ischemic cardiomyopathy. It suggested the following to diagnose ICM (Read REF 2)

  1. LV dysfunction < 40% EF
  2. >Atleast one significant proximal coronary lesion (Usually 2 or more)
  3. With the history of MI or Revascularisation

* We are analyzing our data (Madras medical college, Chennai India) and propose to write WHO/WHF to include the following additional criteria to diagnose ICM.

4. At least 6 months should be elapsed between the MI and diagnosing Ischemic cardiomyopathy,

5. Must have significant LV dilatation & global Hypokinesia(With or without regional variation).

6. At least one episode of clinical heart failure is required before labeling it as Ischemic cardiomyopathy.

Other definitions that endorsed Duke

STITCH criteria *Surgical therapy in ischemic DCM study ICM was defined CAD with cut off EF < 35% with triple or double vessel disease.

iFAQs in Ischemic cardiomyopathy

1. Can we diagnose ICM without a history of MI?

This is tricky. As we all aware its very much possible as in silent MI of diabetes. One more possibility is even chronic coronary syndrome with microvascular dysfunction can lead to ICM.

2. Can Ischemic cardiomyopathy present as HFpEF or RCM?

While most Ischemic Cardiomyopathy present as DCMs with HFrEF, It is currently not clear how much of Ischemic heart failure present as HFpEF and if so they can’t be included technically as Ischemic cardiomyopathy in spite of the fact they present as HF.(as EF would be >50%)

3.When does a Post MI failure become Ischemic cardiomyopathy?

If the definition of STITCH or DUKE is applied, any acute STEMI can fulfill criteria of ICM. Hence it advisable to have a time limit say 6 months following MI to be referred to as Ischemic DCM. Pathologically to call it true cardiomyopathy, scarring, dilatation is required. Myocytes should be in independent self-destruction mode irrespective if hemodynamic conditions.

Response to treatment

The only purpose to diagnose ICM is to try to remove the I from ICM( ie Ischemia) Unfortunately, it is not an easy task. (While correcting Ischemia in ACS seems to be such an easy job.)

Following principles apply.

  • Medical management of HF/Ischemia is the key.
  • It is advisable every patient with cardiomyopathy should undergo coronary angiogram to rule out ICM.
  • Effect of revascularisation remains equivocal.
  • Viability of remaining muscle mass must be documented. (At least one-third of total cardiac mass should be viable.(Not very easy to prove though)One may use Doubutamine /Nuclear stress/PET etc) .It’s very important to realize even if the viability is demonstrated, the area that shows viability must be supplied by an artery that has a revascularisation eligible lesion.
  • STITCH can be called as a negative study (meaning positive outcome for patients if the patient doesn’t receive CABG in mulitvessel CAD and LV dysfunction ).However , STICHES (Extension of stich showed some long term benefits) The probable reason for CABG not helping much in ICM is the muscles didn’t get further useful life, either because it’s fully dead or extremely viable, that revascularisation made no impact.
  • CRT/ICD is known to prevent SCD and improve the functional class.
  • Heart transplantation is a life-modifying specific strategy.

Final message

I agree, many times our valuable time is wasted in renaming /Altering /relabeling a disease /process or pathology without any useful purpose. Medical nomenclature and classifications are done to make diagnosis simpler, choose an appropriate therapeutic modality and make a positive impact on the outcome.

In that sense, segregating ICM from other causes of cardiac failure do help in choosing a specific management strategy.

Let us welcome MOGES, It is the most comprehensive cardiomyopathy classification system (Like TNM classification for cancer). Still, I am not clear why it hasn’t included CAD in that system. Thanks to Dr. Burch who thought of this 50years ago.


1.Burch, G. E., Giles, T. D., & Colcolough, H. L. (1970). Ischemic cardiomyopathy. American Heart Journal, 79(3), 291–292.

2.Felker G.M, Shaw L.K, O’Connor C.M (2002) A standardized definition of ischemic cardiomyopathy for use in clinical research. J Am Coll Cardiol 39:210218

History of cardiomyopathy classification

The landmark thoughts originated in 1972 .When Goodwin and Oakley defined cardiomyopathies as the heart muscle diseases of unknown cause and described them as dilated (DCM), hypertrophic (HCM), and restrictive (or obliterative) (RCM) cardiomyopathy types.

WHO adopted it mostly and suggested Primary and Secondary cardiomyopathy in 1980. In 1995 WHO revised it.

The current MOGES classification doesn’t mention about Ischemic etiology