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Archive for November, 2020

Why AF is often well tolerated in Hypertrophic cardiomyopathy ?

Posted in Atrial fibrillation, tagged , , , , , , , on November 29, 2020|

Up to 25 % of LV filling is done by atrial contraction. Atrial booster function is important in LV outflow lesions. This can be critical in patients who have diastolic deformities of LV. ( an audible or even palpable S4 confirms the atrial kick in these situations )  This is how we were taught for decades right. Still, it may hold good in many left-sided condtions, but in HCM it definitely seems to be not true. 

A succinct review of this topic makes a good read.

Incidence if AF in HCM is about 20% (Mostly paroxysmal 70 % , Persistent /Permanent 30 %)

Mechanism of AF IN HCM

  • Increased atrial wall strain(Proven by strain echo studies)
  • Atrial dilatation
  • Atrial pathology (Atrial myocyte  disarray,  myosin is present in atria too. )
  • Unrelated to HCM (SHT etc)

We can confirm with large observatory data, left ventricle handles AF so well. (Ref 1)The onset of AF, (at the least), is, expected to cause some new worsening dyspnea. Even that is not universal (very surprising isn’t it ?)

Does AF correlate with syncope?  again no is the answer. So it’s the LV outflow behavior that determines the hemodynamics not what is happening at the inflow. Even hard outcomes like heart failure, sudden death, net mortality was not found to be altered much by the lesser chamber fibrillation. But, the only issue relevant here is thromboembolism that has to be taken care of.

How is that AF make little hemodynamic Impact in HCM ?

It is difficult to comprehend this scenario. For this to happen the mean LA pressure should remain within the physiological range even when the atria goes to fibrillation. But it seems distinctly possible as many patients with HCM are not aware of this arrhythmia. The LA pressure-volume loop is an enigma. It is likely LA “v” wave loop can adjust to “a” wave deficiency in an exemplary manner.

Further, the hyper-contractile left ventricle can assist itself by sucking blood in very late diastole (to be precise with the onset of systole )and so it need not really depend on the atrial kick.  A similar phenomenon explains the persistence of presystolic accentuation in the murmur of mitral stenosis. The fact that rate control in AF is able to compete with rhythm control in  AFFIRM/RACE study vouch for the negligible hemodynamic impact between SR/AF.

Clinical implication

  • A well-tolerated AF doesn’t preclude the need for thromboprophylaxis. We must ensure  NOAC/Warfarin in all those with persistent AF.
  • Attempts to convert AF to sinus rhythm with all those Invasive LA mapping and Pulmonary vein is unwarranted if not contraindicated.
  • When ICD is indicated additional  Atrial leads to reduce AF is again becomes reductant. 

Final message

Many of the hemodynamic concepts we have learned over the years could be based on logical perceptions that may not manifest at the bedside. Constant flux in our understanding of cardiovascular physiology is required. 

Reference

1.Rowin EJ, Hausvater A, Link MS, Abt P, Gionfriddo W, Wang W, Rastegar H, Estes NAM, Maron MS, Maron BJ. Clinical profile and consequences of atrial fibrillation in hypertrophic cardiomyopathy.Circulation. 2017; 136:2420–2436. 

 

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ASD device closure: “Mind the gap” to avoid SA nodal artery compression.

Posted in Cardiology research topics, cardiology research topics for fellows, Uncategorized, tagged , , , on November 20, 2020|

The branching pattern of the human cardio-vascular tree is as unique as one’s fingerprint. One such hugely variable anatomy is the SA nodal blood supply.

Certain salient features

  • Variation can be seen in origin, course, and termination.
  • Now it is estimated to arise from RCA in 70% (Moved up from 55% in old studies )
  • From LCX (25%)
  • Dual SA node supply(5%)
  • Direct from Aorta

It is heartening to find this good anatomical review on this topic.

A) From the Right Coronary Artery; (B) From the Left Circumflex Artery (proximal); (C) From the Left Circumflex Artery (distal); (D) From the Left Coronary Artery; (E) From the Aorta; (F) Dual origin from the Right Coronary Artery and the Left Circumflex Artery. Image source : Vikse J, PLoS ONE 11(2): e0148331

Implication for the surgeon

The whereabouts of this tiny, yet important artery is critical to the surgeons’ as they incise and explore the atrial roof. (A gateway, that gives access to so many cardiac surgeries) The SA nodal artery mostly goes retro caval but it can be peri-caval or even anterior to SVC.

This image shows (a,b,c) the course in relation to SVC, Developmentally as the venous pole go posteriorly to fix the SA artery behind it.Image source : Vikse J, PLoS ONE 11(2): e0148331

For the Interventional cardiologist

A rare but distinct mechanical compression of SA node artery is reported with large ASD closure device. The plane of compression is usually occurring in the superior aspect of IAS when the SA node artery cross over the RA to reach the SA node. Should be suspected whenever unusual bradycardia occurs during the manipulation of the device or just after deployment. Always mind the delicate gap  between the antero superior rim and disc where SA nodal artery is likely to trespass.

AV node Ischemia with ASD device

With precise imaging modalities, new secrets are emerging. Additional AV node arteries from proximal RCA is documented.This is a surprising learning point for us. This artery is referred to as the right superior descending artery, which provides an alternative blood supply to the AV node from the proximal right coronary artery. The transient compromise of this hitherto unknown AV nodal twigs by the ASD device cause AV blocks. With this new info, we also got an answer to one more lingering question, why would disproportionate bradycardias are observed in inferior MI even when distal RCA is flowing well. We can’t blame high vagal tone always.

SA node compression by ASD device amplatzer

A CT angiogram showing how the ASD device encroaches the SA node artery. Image Source:Tsunehisa Yamamoto JACC 2016 (Linkedbelow)

The original article has an excellent video clipping of how an ASD device hugs the SA node at the superior edge of ASD.

Final message

Human anatomy is not the subject meant to be read in the first-year medical school cadavers, & forget thereafter. Surprisingly. the field of anatomy is also evolving with new mysteries exposed by modern imaging.SA nodal arterial blood supply is one such interesting aspect of cardiac anatomy. Young fellows in cardiology shall pursue further anatomical dark spaces in the heart (One such topic is how cardiac lymphatics compete with the venous system in draining cardiac interstitium)

Reference

Vikse J, Henry BM, Roy J, RamakrishnanPK, Hsieh WC, Walocha JA, et al. (2016) AnatomicalVariations in the Sinoatrial Nodal Artery: A Meta-Analysis and Clinical Considerations. PLoS ONE 11(2): e0148331

It’s gratifying a unique and committed group exclusively doing research in Anatomy. It Department of Anatomy, Jagiellonian University Medical College, Krakow Poland.

http://www.eba.cm.uj.edu.pl/

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Corona second wave might bring some good news !

Posted in Uncategorized, tagged , , , on November 17, 2020|

Corona has triggered the scare of the century, even among the scientifically savvy brave men & women. The scale of the panic was unprecedented. However, one positive outcome of this pandemic was, this 20 nm RNA particle forced many of us, to ponder over the true purpose of life. It demanded a course correction in those who found one. Now, after 9 months Corona, in its second wave seems to be somewhat kind to humanity. The case fatality rate is dropping to nearly one-tenth of its peak in the first wave. 

 

 

 

 

Where is the evidence coming from?

Apart from our own personal experience from 1500 bedded corona hospital, this paper reports data from 53 countries.

 

Note, the red covid mortality curves are not matching the black positive waves (Both Europe and Asia)

Link to the original article https://doi.org/10.1111/tbed.13819

The possible reasons for the low case fatality rate.(Personal observation)

  1. Viral apologetic  behavior*
  2. Second wave affecting more healthy younger who fight it better.
  3. Less panic in the health care delivery system
  4. Though there is no specific therapy, at least some basic treatment strategies are in place.(Timely steroids & mindful oxygen did the trick)
  5. Initial aggression out of Ignorance (ie ventilator deaths) has largely ceased.
  6.  RT-PCR(which helped In diagnosing /isolating ), CT scans,(helped in grading) the Remdesvirs(gave peace of mind ) the Tocilizumab(did nothing great ) has at best played a minuscule role at a huge cost.

Among all these factors, which do you think is the most important contributor to a declining fatality?

The single important factor could be, “The virus has decided unilaterally to forgive the frightened human beings, and become less virile“.(At least in those people who sincerely respected the viral might by wearing masks and other paraphernalia) Sorry, for uttering this forbidden stuff in science, still it could well be the truth. 

If corona is losing its sting & steam what would be the realistic role of the vaccine? What is the likelihood of vaccine getting false credit*?If we are allowed to be optimistic, Corona in all likelihood is waiting to say goodbye after a feeble third or fourth wave. All these are speculative, still, one thing looks positive. Unlike the much-quoted fact about the Spanish flu of 1920, which resulted in more damage in the second wave, which is unlikely to happen with corona.

Disclaimer

* This article never intends to undermine the importance of preventive measures and vaccines for this worst pandemic in recent human history.

Counterpoint 

The decline in case fatality is may not be uniform as fresh data from Europe suggest. It’s hyperbole to expect corona’s second wave to bring good news. It is largely left to the people’s behavior to contain the pandemic than to get a pardon from the virus. 

 

 

 

 

 

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Arrhythmia basics: How often we need to know the mechanism of arrhythmia ?

Posted in Basic science -Physiology, Brugada syndrome, cardiac electrophysiology, cardiology -Therapeutics, Cardiology-Arrhythmias, tagged , , , , , , , on November 2, 2020|

How many times you have treated cardiac arrhythmia in both emergency & non-emergency situations?

Infinite times.

How many times did you really bother to know the mechanism of a given arrhythmia before ordering medication or shocking?

Hmm,.. let me think. (Except for AVNRT/ AVRT, and few VTs, very rarely I have worried about the mechanism  !)

Why is it so? because treatment takes priority and we are able to tame the arrhythmia even without knowing the real mechanism.

The following slide is a gross summary of the cardiac arrhythmia mechanism

Understanding cardiac arrhythmia is vitally important for a few reasons in a few settings.

  • In acute settings, we need to know automatic tachycardias will not respond to shocks. Reentry tachycardias will respond more promptly. (Of course, we may not know it till we shock ) Calcium blockers like verapamil might block triggered activity in MAT. Overdrive pacing is the answer for many automatic tachycardias and some refractory reentrant tachycardias (ATP protocols in ICD has taught us this ) 
  • In the chronic setting when you contemplate mapping, locating, and ablating arrhythmias, mechanisms are important. The task here is locating slow conduction paths and decoding the diastolic circuit around the scar  (If you plan ICD, knowledge about mechanism  becomes redundant again)

  • Finally, knowing the mechanism of arrhythmia is a fascination by itself to help understand the great subject called cardiac electrophysiology, where 100s of ion channels work nonstop drawing the action potential on a moment to moment basis sustaining our life.

A challenge

Can you localize a VT and find the mechanism in a patient who is Ischemic /hypoxic and acidotic? You can never do it. Please note, most polymorphic VTs can’t be localized. The mechanism is either automaticity, trigger activity, or even micro-reentry. You need to shock and look for the causes.(Link to How does the treatment of monomorphic VT differ from Polymorphic VT? )

Final message

Should we need to know about the mechanism of arrhythmia we treat?  Definitely yes, if you have that passion to know the truth, or else just order Amiodarone or shock and check out of CCU. (Of course, we have a very good option of calling EP consult the next day.)

 A review article on mechannism of cardiac arrhymias

Rev Esp Cardiol. 2012;65(2):174–185

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Acute Aortic syndrome : Please mind the length of “Ascending Aorta” as well.

Posted in aortic aneurysm, tagged , , , , on November 1, 2020|

 Aorta probably is the most critical structure in the entire circulatory system. (apart from the heart of course !) It is a 1.5 to 2.5 mm thick tube, with a diameter of 2.5 cm/length of 30 -35 cm from the aortic valve to the iliac bifurcation.(Eric Borsero 2011) It handles about 7500 liters of blood every day. Understanding the Aortic pathology has vastly improved at the molecular level with deep gene sequencing that defines fibrillin phenotypes.  Meanwhile, CT ,  4D MRI and 3D prototyping have landed us in a new era where we can feel the exact models of a patient’s virtual aAorta for monitoring and treatment purposes.

 

While acute Aortic syndromes is the one that bothers us most, even chronic aortic enlargements are equally risky as at any time it can become acute. Though the risk of aneurysm and rupture is related to the histology and molecular disruption at the level of aortic media, we can only rely easily on is its dimension. Traditionally we bother about the diameter since it is the aortic radius that Influences the stress through to Laplace law.(Wall stress equals twice the radius /Thickness of wall)

Click over the Image for ESC Aortic disease guidelines

The annulus is the narrowest part, it gains about 50% width (10mm) at the level of the sinus of Valsalva to reach about a maximum of 35 mm and again narrows at ST to a junction (almost to the same diameter of the annulus) It continues further as ascending, arch and descending aortas with gradual tapering. 

Risk of rupture

Are you aware aorta keeps growing with age?

Unlike many other organs, growth of which gets arrested by adulthood, aorta appears to grow well into middle and elderly age.The aorta grows by 6cm in total length between age 20 to 80 (Ref 1)   The average growth of the ascending aorta is .18mm /year

This fact was reported 70 years ago Dotters famous study Circulation 1950  https://www.ahajournals.org/doi/pdf/10.1161/01.CIR.2.6.915

I used to wonder in many elderly why chest x-ray shows wide superior mediastinum still echocardiogram didn’t show any dilatation.This we call it as aortic unfolding. The term unfolding of aorta may represent the elongation of both ascending and descending aorta. The mechanism is due to multiple factors, like lax ligamentous of aortic attachment, dilatation, and longitudinal elongation.

Unfolding of the aorta . (How to measure unfolding Lee JW, (2014) Aortic Unfolding Determined Using Non-Contrast Cardiac Computed Tomography: Correlations with Age and Coronary Artery Calcium Score. PLoS ONE 9(4): e95887. )

How Important is the length of the aorta?

Risk of Aortic aneurysm is usually attributable to the diameter (Accepted normal 2.1cm/m2) . However, in IRAD registry, 50 % of aortic dissection happened in aortas less than 5 cm. So there is something more than the diameter that confers the risk of an aortic event. Is it the length and elongation?  After years of observation, we now realize it is indeed true. It is a surprise we didn’t realize  elongation of aorta also confers the same aortic wall weakness like that of Increased diameter (Longitudinal deformation/Stretch )

How to measure the length of Aorta?

It is best measured by CT scan or MRI. There is a new parameter called  Wu Index, which is based on both length and width of the aorta , which predicts the risk of aortic event. 

 

 

Jinlin Wu, Mohammad  Zafar, Yupeng Li,  J Am Coll Cardiol. 2019 Oct, 74 (15) 1883-1894.

Final message 

Aneurysm of the aorta is traditionally defined based on the degree of dilatation. It’s time, Aortic length should also be included in defining aortic aneurysm. We need to monitor it periodically as well in the population at risk. 

Reference 

1.Adriaans BP, Heuts S, Gerretsen S, et al. Aortic elongation part I: the normal aortic aging process. Heart 2018;104:1772–7.

2.Ascending Aortic Length and Risk of Aortic Adverse Events  Jinlin Wu, Mohammad  Zafar, Yupeng Li, 
J Am Coll Cardiol. 2019 Oct, 74 (15) 1883-1894.
3.Pape LA, Tsai TT, Isselbacher EM,  Aortic diameter > or = 5.5 cm is not a good predictor of type A aortic dissection: observations from the International Registry of Acute Aortic Dissection (IRAD). Circulation 2007;116:1120-1127
 
The comprehensive reference 

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