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Posts Tagged ‘hypertrophic cardiomyopathy’

Hypertrophic cardiomyopathy (HCM)  is the most common primary disorder of cardiac muscle. The incidence is about 1 in 500, which would mean 1.5 crore HCM patients will be living on our planet at any moment. The root cause of pathology is located in 20 odd genes that define cardiac muscle protein integrity. (Myosin, Troponin, Titin, etc) This leads to the bizarre architecture of cardiac muscle, prone to progressive fibrosis.(Paradoxically, 90% of HCM have normal or supernormal contractility till very late stages, proving that the much-dreaded term myocardial disarray has little effect on contractility. It is all the more funny, as we strive hard to suppress this excess contractility caused by disarray with beta-blockers.

SCD is the scary face of this disease. If the incidence of SCD is less than 1 %  per year, do a little maths to know how many will succumb every year to this disease. However, It is the symptoms like exertional dyspnea (most common,) followed by syncope and rarely angina that bring HCM  patients to the physician. Though the pathology is diffuse and global, I don’t understand why we got stuck with the outflow tract gradients and dynamic obstruction. HCM is an equally a disorder of LV inflow obstruction (rather a restriction). It can be presumed myocardial disarray makes more impact on diastole than systole. The relationship between inflow and outflow gradient is a poorly explored area in HCM. Detailed analysis of E and A velocity profiles along with tissue Dopper will throw more light in symptomatic patients. 

 

 

The importance of LVOT gradient in HCM was questioned by Criley more than 30 years ago.

There may not be many takers for this concept in spite of our realization, that the major symptom of HOCM is not due to outflow tract obstruction. Further, sudden cardiac death risk is not fully negated by drugs and surgical myectomy. Christopher J. McLeod EHJ 2007) No surprises we require the help of ICD to tackle the SCD risk even after the relief of obstruction.

How to measure the gradient in HCM?

Image source: .Jeffrey B.Geske  Assessment of Left Ventricular Outflow Gradient: Hypertrophic Cardiomyopathy Versus Aortic Valvular Stenosis  JACC: Cardiovascular Interventions  Volume 5, Issue 6, June 2012, Pages 675-681

  • Continuous-wave Doppler is to be used for net LVOT gradient.
  • Pulse doppler to analyze regional, local gradient profile within LV chambers
  • HCM we need to follow up with peak gradient unlike valvular AS  because unlike valvular AS gradient  is not uniform to be differentiated for MR jet (Ref Jeffrey B.Geske Mayo clinic )
  • The lobster claw pattern (M V Sherrid  JASE 1997) is academically exciting, as it documents the sign of obstruction. (Please note,  pulses bisferiens is clinical lobster claw bite, felt in the neck )
  • This is the only entity “standing echo” to be done. compared to sitting and semi-supine position.(Stand echo is the simplest provocation )
  • Chronic BB therapy does reduce the gradient.(There is some evidence, disopyramide beats BBs for this purpose ) 
  • Associated systemic hypertension can influence the gradient in a complex manner(meaning either under overestimate )

How to provoke gradient if the resting gradient is low.

  • Valsalva maneuver 
  • Post VPC
  • Excercise

Dountaimine stress test should not be used as it can generate pseudo gradients. Should we provoke otherwise asymptomatic zero gradients healthy HCM? It is debatable and can be an unsolicited invitation to imaginary troubles.

Importance of MRI: Morphology can be more important than gradient 

It has now become a dictum every patient of HCM must undergo MRI. This not only helps to define the morphology of LV, different subsets of HCM, and risk of SCD , it also guides the surgeon where exactly to resect,  and how much mass of myocardium to be removed. MRI defines mitral valve anatomy more clearly and helps whether AMl plication is required or not in addition to myectomy.(Elongated bulky Mel is competing for space in the narrow corridor of LVOT, you know ) MRI clearly helps to avoid over-enthusiastic alcohol septal ablation as well. 

Principles of management  

  1. Symptom reduction, risk estimation, SCD risk reduction, and correcting associated arrhythmias like AF /VPDs, etc.
  2. Beta-blocker help relieves symptoms and control most  VPDs or AF. No drug effectively eliminates the risk of SCD. (But, I doubt it’s wrong, BBs must have a positive impact on this we are failing to prove it ).
  3. ICDs are promoted as a mainstay to prevent SCD.It should be emphasized ICDs can’t reduce the troublesome exertional dyspnea of HCM.It simply prevents(expected to prevent ) SCD after allowing the VT/VF to occur. (ICD do come with its own morbidity  and anxiety, Sub-cutaneous ICD is just beginning to be popular, doesn’t have VT control though no ATP algorithm ) 
  4. Surgery regresses LVOT gradient and regress symptoms still may be the best option (Dual-chamber pacing, alcohol ablation, (now RF) are mostly interventional excesses with unproven worthiness. Additional mitral valve repair strategy during myectomy has some proven value.
  5. Mavacamten (the proposed new magic drug ) is shown to steer and stabilize the two-headed myosin interaction with actin , thus reducing the force of contraction at the same time not inhibiting it truly. The mechanism is great on paper, let us see the follow up of EXPLORER study patients)
  6. Counseling  & reassurance( The real risk of SCD is far less than the fear of SCD.I have seen the relatives of HCM patients are more worried than HCM patients with a 30mm IVS. This is amplified by a crazy battery of genetic tests with dubious predictive value. In my opinion, one need not do this even as the current guidelines trying hard to make it appear as a pleasant  affair)

Final message

We are taught right from our early days in medical schools, HCM is synonymous with dynamic LVOT obstruction. However, to hang our thoughts exclusively on this hemodynamic concept lands us in management errors. Let us learn to look beyond  LVOT gradients in HCM. We need to look at the overall morphology of LV, mitral valves, LA dynamics, etc. Please realize, there is a huge mass of myocardium sitting silently not eliciting any gradients, still good enough to cause symptoms and dictate the natural history. 

Reference 

1.Jeffrey B.Geske Michael W.Cullen PaulSorajja  Assessment of Left Ventricular Outflow Gradient: Hypertrophic Cardiomyopathy Versus Aortic Valvular Stenosis  JACC: Cardiovascular Interventions  Volume 5, Issue 6, June 2012, Pages 675-681

Postamble

For the pure academics, please read this.The ultimate advisory from the authoritative source. 

 

 

 

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Hypertrophic cardiomyopathy (HCM) is the most common primary cardiac muscle disorder.It is one of the  extensively studied medical  entity in terms of pathology, genetics, electrophysiology and treatment.Though it has dramatic myocardial  phenotypic expression , longevity  can be near normal  except in a minority who are prone for LV dysfunction and SCD due to the indirect electrical instability.These arrhythmia arise due to myocardial disarray , micro vascular disease or fibrosis.

NSVT  by definition is runs of VT at a rate of > 100 /mt occurring less than 30 seconds.

How common is NSVT in HCM ?

On Holter study with  178  patients  with HOCM (Adabag  JACC 2005 ) 90 % showed VPDs

  • 12%  > 500 VPDs/24 h
  • 40% had couplets,
  • 30% had non-sustained ventricular tachycardia (NSVT).
  • Over a follow-up of 5.5  6% patients died suddenly (annual mortality rate, 1.1%)

For sudden death, NSVT on Holter ECG had negative and positive predictive values of 95% and 9%, and sensitivity and specificity of 45% and 69%, respectively.

nsvt incidence hocm

In this series from StGeorge hospital London from 630 patient incidence of NSVT was 19% and 4 episodes were observed in 48 hr in most .Monserrat L, JACC 2003

What is the duration , How fast  and  how frequent is the NSVT ?

It is expected the total burden of NSVT would have a definite impact on outcome.  Curiously the duration, fastness and frequency of NSVT  was  not related to prognosis in atleast one study (Monserrat L, JACC 2003)

Relationship between age and burden of NSVT ?

Aging has a sobering effect on these ventricular ectopic activity by probable conditioning and fibrotic interruption of electrical activity.

How often a episode of NSVT  convert to VT ?

Considering the day to day even it should be termed extremely rare . Even among person who survived an SCD the next episode of VT can be very rare.

What is the current Indication for ICD in HOCM ?

Secondary  prevention (Consensus > Controversy )

Primary prevention (Controversy > Consensus – Still evolving )

Questions galore  . . . answers struggle !

Does NSVT arising from single focus or multiple focus ?

What is the relationship between NSVT and degree of obstruction ?

What is the relationship between NSVT and MRI detected myocardial scars ?

How effective is beta blocker suppress NSVT ?

Can we implant ICD for only NSVT ?

Is it true  ICDs add more anxiety , distress and harm  than the index disease ?

How to program ICD to ignore  NSVT and fire only for VT ?

For further information , refer this most authentic knowledge base. esc guidelines hocm

Final message

Predicting which NSVT will go for SCD  in HOCM can be as difficult as predicting the next major earth quake  that would strike the pacific rim that  experiences unrecognized tremors  on everyday basis .We have learned to live with that right ? So it appears NSVT is more of a nuisance arrhythmia for both the patient and physician .

Still , science demands identification  individuals  with highest risk for arrhythmia . How to do it ?  Is it the  morphological features  , degree of obstruction  or  genetic finger prints. It is still not resolved . One thing is clear we can’t advice ICD for all those with runs of NSVT  for perceived fear or pressure from peers or industry !

 Referene

 

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Hypertrophic cardiomyopathy(HOCM)  is a relatively common inherited myocardial disease.Since it predominately involves  LV myocardium and we know LV muscle mass is an integral part of  mitral valve apparatus , it is natural HOCM  has a major  impact on   mitral valve function .

The mechanism  of MR in HOCM is attributed to the following .

  • Asymmetric septal hypertrophy (ASH ) related abnormal pap muscle alignment (Geometric distortion  )
  • Exaggerated SAM(AML  is attracted towards LVOT with every systole that tend to  keep the mitral  valve  unguarded and MR results)*
  • Intrinsic abnormalities of mitral valve.
  • Associated MVPS
  • VPDs and Non-sustained VT can result in transient MR
  •  Pacemaker mediated MR (DDD pacemaker was used to induce desynchrony of LVOT vs LV free wall .This  concept  is almost a failed  one now !)
  • End stage HOCM -Left ventricular dilatation

* This mechanism is considered less important ,  as SAM is almost universal in HOCM  but MR occurs in less than 20%  patients with HOCM.

Eccentric MR vs central MR

In HOCM the MR is more often eccentric .This is understandable as the primary mechanism is related to faulty angle of pap ,muscle vs leaflet attachment.

If SAM is primary mechanism jet is directed posterior.

Murmur of MR in  HOCM

Is rarely pansytolic as the mechanism of MR begins to operate well after the systole starts .

Many times it is difficult to differentiate LVOT murmur from MR murmur . Th ever confusing and tentative  maneuvers might help in few shrewd cardiologists.

Issues  during echocardiogram

Very often MR jets are mistaken for LVOT gradient.Ideally two gradients in isolation (or  overlapping each other)  one bell shaped other dagger shaped must be documented.

Please note : LVOT jet is different from MR jet in size, shape, timing and site of maximum signal . Still it is often be confused with one other. Most common reason for this is technical .A careful apical 4 chamber view with well opened LVOT will reduce the error . Never record a HOCM echo without ECG gating . The MR jet may be very trivial in color flow but doppler will still pick the signal well . Realise ,for hemodyanmic reasons MR jet must be always more than LVOT jet.Finally if you get a report a LVOT gradient > 100mmhg in HOCM suspect it to be MR ! More often your suspicion will prove to be right !

Can mitral regurgitation occur in non obstructive HCM ?

Yes , in few . This is due to intrinsic abnormalities of mitral valve .

What happens to MR with surgical correction ? Can medical management  regress the MR ?

It is expected to regress.But many patients don’t. Effect of beta blockers   on MR severity is not studied well.

Management

  • Most cases of MR  do not require specific intervention.Just reassure them.
  • Correction of LVOT obstruction is expected to relieve MR considerably.
  • Intensive beta blocker or calcium blocker can regress the MR.(Negative inotropy)
  • Mitral valve repair may be necessary in few  with re-engineering of pap and chordae .
  • Mitral valve replacement should be a last resort. It  may be highly tempting  .But restraint is warranted. Much  damage has been done by showing undue haste in replacing mitral valve in HOCM

Final message

It needs to be realized whatever we do  for the HOCM patients , the ultimate outcome is determined by the quantum myocardial disarray  the patient has inherited from their parents.The myectomy , the alcohol ablation, mitral valve repair,  DDD pacing , beta blockers all are palliative. Except a few  , most HOCM patients generally live their natural history .

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