Posted in cardiac surgery, Cardiology - Clinical, cardiology -Therapeutics, tagged artifitial valve, ball and cage prosthetic valve, bio prostehtic valve, starr edwards valve on September 29, 2011| Leave a Comment »
The prosthetic cardiac valve which saved so many lives in the later half of 20th century is no more. A valve which is not only known for its excellent durability but also devoid of sudden mechanical occlusion , unfairly lost its place by the rival mechanical bileaft valves. (Supposedly superior hemodynamics !)
Here is a nice video from Indian surgeon which describes the hardware of Starr Edwards valve .
Please read a related article from my site
Posted in Cardiology - Clinical, cardiology -Therapeutics, Cardiology hypertension, cardiology innovation, echocardiography, Hemodynamics, tagged atrial alternans, doppler echocardiography, e and a velocity swings, mitral inflow alternans, newer concpets in diastolic dysfunction, non respiratory swings in mitral e velocity, pulsus alternans, recent advances in diastolic dysfunction on September 28, 2011| 1 Comment »
Heart is a dynamic organ . It can alter its force of contraction with every beat according to the needs.Generally it responds to length of previous diastole.This is famously called frank starling law , ie the force of contraction is directly proportional to the end diastolic fiber length. So changing diastolic duration as in atria fibrillation classically result in varying amplitude of LV contraction and pulse volume.
However , the commonest cause for pulsus alternans is due to severe left ventricular systolic dysfunction .There has always been a suspicion about the existance of beat to beat variation in diastolic function as well. We have recently observed a new* explanation for pulsus alternans .We know AV inflow is subjected to respiratory swings . Non respiratory swings in mitral and tricuspid valves are rarely described. This pattern is now increasingly recognised.
These non respiratory swings in the mitral inflow doppler pattern is seen in some of the patients with hypertension and LVH.This probably confirms the existence of beat to beat variability of diastolic function . This phenomenon is relatively a new observation . Such pattern are common in patients who have had a recent hypertensive failure .
Here is a doppler of mitral inflow recorded from a patient with hypertension with LVH .
This is the doppler mitral inflow profile of a patient with Hypertension, LVH and class 2 dyspnea .Note the non respiratory swings in both "e" and "a" velocity
It is proposed to define a new class of diastolic dysfunction that can be referred to as diastolic mitral inflow alternans .This phenomenon probably indicates a more severe grade of diastolic dysfunction.At the molecular level this is related to undulating flux in the calcium uptake from cytoplasm into SERCA .There is one more possible explanation for diastolic alternans -Left atrial dysfunction .
Occasionally one can visualise a chaotic pattern of diastolic filling waves (e=a e>a a> e ) Such patterns are thought to be markers of impending acute diastolic shutdown .
Further analysis of this mitral doppler inflow pattern will be reported later.
Reference
* Though we observed this for the first time , this is not a new phenomenon .There are few reports available in the literature.
http://www.sciencedirect.com/science/article/pii/S0735109785800358
http://www.sciencedirect.com/science/article/pii/S0894731706012818
Posted in cardiac surgery, Cardiology - Clinical, cardiology-Anatomy, tagged aortic regurgitation, aortic root in bcav, bcav, bicuspid aortic valve, congenital bcav, l +n fusion in bcav+aortic stenosis, non coroanry cusp, premature degenration of aortic valve, r + n fusion bcav, raphe in bcav, right and left coroanry cusp fusion, significance of raphe in bcav, valve analgen on September 27, 2011| Leave a Comment »
Bicuspid aortic valve (BCAV) is one of the common congenital abnormality of heart . Incidence can be 1-2% of population . It can result in premature aortic degeneration with Aortic stenosis/Aortic regurgitation or both .
The normal development and arrangement of three cusps is altered ( rather interrupted ) during fetal life.
There can be two ways BCAV can occur. One is due to the fusion* of two leaflets to covert a tricuspid valve into bicuspid , and the other is two cusps develop de novo .The former has a raphe , while the later has no raphe.
The fusion* occurs between either
(* The fusion is embryological , not acquired )
Most often the fusion is due to lack of division in the valve analgen .Hence a raphe (A conjoint remnant) is noticed .
90% of BCAV has raphe ,only 10 % lack raphe . Aortic root is also structurally abnormal in many .(Little clinical sequale though !)
Coronary artery origin anomalies are more common with BCAV. We also know co-arctation of aorta has a embryological link with BCAV.
The commonest type of BCAV is
The most hemodyanmic stressed BCAV is R +N type fortunately it is rare
R + N fusion is a high risk BCAV as degeneration occur fast
The least common type is
The coronary artery origin anomalies are common
BCAV in the absence of raphe is classified separately (This constitutes 10 % of all BCAV)
The nomenclature is
What is the pathological significance of raphe ?
Many believe presence of raphe accelerates degeneration as leaflets have rough surfaces . Still , BCAV with raphe has less coronary anomalies and aortic root pathology .
Presence of raphe indicate relatively a minor embryological defect , as the fault is in the failure to divide after the formation of analgen , while BCAV without raphe imply lack of development of analgen itself . This is expressed in the coronary sinus anatomy and aortic root dimension and orientation .
So currently it is welcome to spot a raphe in the patient point of view .Echo cardiogram is notoriously unreliable to diagnose raphe. Once degeneration process sets in , it is almost impossible to recognize the presence or absence of raphe .
* Please note ,tricsupid aortic valve with eccentric leaflet closure shares a close pathological relationship with BCAV. Premature degeneration , (AR more common than AS here ) .This entity will be discussed separately later.
Image courtesey
Part of the Image (The valve) is adopted from Yale university Image Bank .
Posted in Cardiology - Clinical, Cardiology -Interventional -PCI, Cardiology-Coronary artery disese, Infrequently asked questions in cardiology (iFAQs), Top ten in cardiology, tagged limitations of coronary angiogram, optical illusion in cath lab on September 26, 2011| Leave a Comment »
Coronary angiogram is a videographic snap shot of moving targets. Coronary arteries are dynamic , tortuous vessels of varying dimensions .Normal vessels sometimes appear as an illusion of lesions and tight lesions may appear innocuous at times. So the rule is never rely on a single view before reporting.
This is an angiogram of a patient , which one of my fellows referred to as “a black pearl inside the LCX !
The same patient,s angiogram showing origin of OM1
Final message
Beware of radiological artifacts in various angiograms. It can lead to erroneous interpretation and interventions !
Posted in Cardiology -Interventional -PCI, cardiology-Anatomy, tagged abberrant rca, anatomy of coronary artery, anterior and posterior interventricular groove, can coroanry artery run away from groove, coronary artery atrio ventricular groove, coronary artery course, left atrio vntricular groove on September 25, 2011| Leave a Comment »
It is a well known anatomical fact the grooves in the heart
sincerely carry the main stem of right and left coronary artery . It can be compared to a train running with dedication on its track .
Image source : AJR June 2007 vol. 188 no. 6 1665-1674
But God has not enforced strict rules especially in human biology . The coronary arteries in few individuals wander away from the grooves.
This is very common for Left circumflex , followed by RCA. It is relatively for LAD to jump out of its groove.(Except in rare Dual LAD system)
Here is a right coronary artery which enjoys its journey outside the right AV groove for a good distance , only rejoin the groove at the crux.
Importance of “Non- Grooval” coronary artery
It is true large diagonals and OMs ,ramus do run without any special tracks . But , it becomes ab entirely different issue when the main stem of RCA,LCX or LAD itself derail from its groove. There is no fixing agents or vascular sheaths that keep the coronary arteries within the groove. Surgeons tell us circumflex is often absent in its groove.
Note the stress and strain on the mid RCA : What will happen if that segemnt requires a stent ?
Hemodynamic implication of such free flowing non grooval coronary arteries is not been studied much .It is also observed these coronary arteries show a tortuous course.This is important for the interventionist as stenting these segments is fraught with excess mobility and tortuosity induced crimping .
Final message
The prevalence of such drifting coronary arteries from its groove can be much more prevalent than we would believe . The anatomical and physiological , surgical issues need to be explored.
Posted in Cardiology - Clinical, Cardiology -Interventional -PCI, tagged a vs v waves, cardiac hemodynamics, central venous pressure, compliance of left atrium, compliance of right atrium, left atrial pressure wave forms, left atrial v waves vs right atrial v waves, pressure curves of heart, right atrial pressure wave forms on September 24, 2011| 4 Comments »
We know the atrial pressure wave forms vary between right and left atrium .In the right atrium “a” waves are prominent and taller than “v” waves, while the reverse is true in left atrium .
Typical filling pattern of Right side chambers .Note The tall A waves . Source : http://www.ncbi.nlm.nih.gov/books/NBK2213/
Note the left atrial a waves are diminutive and v waves are tall .The dark black wave is pulmonary venous waves. Source :http://heart.bmj.com/content/89/2/231.full
The reasons for tall left atrial v waves are
(*Thickness of RA -2mm, LA -3mm )
Related article .
What is left atrial pressure volume Loop ?
http://www.wellsphere.com/heart-health-article/left-atrial-pressure-volume-loop/1208152
Posted in Uncategorized, tagged epicardial brekthrough, how to recognise multiple focus in a VT, monomorphic vt, multifocal ventricular tachycardia, multiform vs multifocal vt, polyfocal vt, polymorphic vt, torsades de pointes, unifocal ventricualr on September 23, 2011| Leave a Comment »
Ventricular tachycardia can be classified in a variety of ways. Monomorphic VT and polymorphic VT is one such classification based on VT morphology.Polymorphic VT generally conveys a meaning of origin from multiple focus .But in reality bulk of the polymorphic VT originate from a single focus . 
How does a single focus have a multiple QRS morphologies ?
This is possible because , even though VT arises from a single focus , the route it takes to exit from the myocardium is different and hence they inscribe different QRS morphology for each beat. It is also possible , as the conduction time varies with each exit route the VT becomes irregular. This phenomenon is called polymorphic VT.
It is assumed the VT focus is often located in the sub endocardium and breakthrough occur in the epicardial side as we record the activity in the surface ECG. Electrophysiology of VT is not that simple , focus of VT can be anywhere , the focus can be single or multiple and exit pathways can also be multiple it and it may even exit into endocardial cavity . Please note , even a single electrically abnormal cell shall act as a focus . To confuse us further , some of VTs may not exit at all , extinguishes before reaching the surface.
It is a difficult job to fix a given polymorphic VT to arise from a single focus or from multiple focus . Multifocal VT can be diagnosed with confidence only after a through electro physiological study.Clinically few clues are there. Electrolytic disorders and ischemia are usually multifocal, while scars VT gives single focus .Other famous example of polymorphic VT are Torsedes de pointes .
Polymorphic VTs are usually hemodynamically unstable but it is not a rule. Surprisingly ,some of the polymorphic VTs are well tolerated . This is especially common in multi focal polymorphic VTs which are hemodynamically and electrically better off . Ironically , presence of multiple focus may be a blessing as they compete with each other , in the process pulling down the other focus from triggering a VF . It is possible one focus acts like a natural anti tachycardia pacing for a VT from another focus.
Ventricular fibrillation can be termed as an extreme form of irregular polymorphic VT as the wavefront breaks into innumerable fragments each exiting the myocardium at will in a random fashion bringing ventricles to a standstill.
Final message
The term multifocal polymorphic VT is generally been abandoned at the bedside as distinguishing it from single focal polymorphic VT is a difficult task*.Still the concept of multifocal VT is alive and kicking in the EP labs , giving sleepless nights to our Electro-cardiologists!
*Please note , multi focal VPDs can be recognised with ease by different coupling intervals, but it is difficult to identify during a run of VT .
Posted in Cardiology - Clinical, tagged chronic pulmonary low flow states in tof, dyspnea in valvular pulmonary stenosis, exertional dyspnea in tof, Mechanism of dyspnea in tof, mechanism of dyspnea in vps valvular pulmonary stenosis, pulmoanry fucntion test in tetrology of fallot, pulmonary microvascualr dysfucntion in tetrology of fallot, tetrology of fallot, ventilation perfusion mismatch on September 22, 2011| Leave a Comment »
It is a combination of biochemical and pulmonary receptor mediated dyspnea.
1. Hypoxia gets accentuated on exertion and it stimulates chemoreceptors located in brainstem as well as aortic arch and its branches.
2. Equally important is the ventilation /perfusion mismatch that occur during exertion as the pulmonary blood flow significantly drops while the lung will continue with normal ventilation .This increases the Vp/Vq (> 1) and worsen the hypoxia and can independently trigger the sensation of dyspnea due to stretching of airway mechanoreceptors..
(It is prudent to recall ,the later mechanism (Vp/Vq mismatch ) is explicitly involved in isolated valvular pulmonary stenosis .Here , there is no admixture mediated hypoxia , still the patient experience significant dyspnea due to meager reduction in pulmonary blood flow.)3. Further , there are some morphological changes that occur in pulmonary vasculature in patients with TOF.This is due to chronic hypoxia as well as “chronic low flow” mediated vascular reactivity. Micro vascular dysfunction in the alveolar capillary bed is possible in TOF. There is some evidence to suggest pulmonary gaseous exchange is impaired when compared to normal lungs.This can also contribute to the dyspnea in TOF.
Reference
The following article excellently describes the pulmonary dysfunction that occurs in patients with TOF .It is prudent to note ,the abnormal lung function fails to get corrected even after total surgical correction in many.
http://onlinelibrary.wiley.com/doi/10.1002/ppul.1950160106/abstract
Posted in Cardiology - Electrophysiology -Pacemaker, tagged 85cm pacemaker lead, Ellestad, epicardial vs femoral permanet pacing, pacemaker generator in groin, pacemaker implantation alternates, pacemaker upper limb dvt, permanent pacing through femoral vein, ppm thorugh iliac veins, svc thrombosis and permanent pacing, venous access for permanet pacing on September 22, 2011| 1 Comment »
Venous access for permanent pacing can be troublesome . Especially with anomalous subclavian , second implantation ,obese patients with upper limb DVT . Temporary pacing through femoral vein is a well known concept.
Here is a concept of implanting the PPM through femoral vein , in the upper thigh and the pacing lead all the way reaches the right ventricle .There were few issues which were thought to be critical .As patients ambulate there could be more generator motion than the sub pectoral location .(By the way , upper limb movement is equally common daily living is isn’t !)
Surprisingly excess motion is rarely an issue . Even dual chamber pacers were implanted through femoral approach.Implantation procedure are simpler than one would have thought and complications are less as well .Since most of the leads are now screwing type and actively fixed dis-lodgement is never an issue.
Final message
The femoral venous access can be considered in all in whom SVC approach is difficult or not possible . 85cm lead is ideal . It is routinely available.
Always consider trans-femoral approach whenever you encounter difficulty in subclavian . Falling back on epicardial approach in such cases should be avoided at all cost. After all , epicardial approach is a major procedure.
Unfortunately, very few centers practice transfemoral modality for PPM right now . Brazil has some experience I understand.Royal Brompton hospital ,London , Memorial heart institute ,Long beach , California have advocated this approach with good success.
We Indians , have a huge potential to propagate this useful concept.I wonder why Femoral – IVC approach could not be a first choice for permanent pace maker implantation especially in small children and adults ! The main issue is not technical , it is more of perceived fear and reluctance to change the tradition.
Reference
Posted in Cardiology -Interventional -PCI, cardiology -Therapeutics, cardiology- coronary care, Cardiology-Coronary artery disese, tagged geographical miss, poba during stemi, primary pci, stemi, stents with radial strength, stentys apposition trial, wall stents for priamry pci on September 21, 2011| Leave a Comment »
During primary PCI , the weakest link for a cardiologist is , he is never sure whether the metal jacket has covered the entire disease segment with optimal apposition . (Geographical miss is another issue !)
This is because , even though the inflation pressure is uniform within the balloon , the required apposition pressure is not the same .This is obvious as the lesion surface has a varying consistency and uneven surfaces . It is a huge guess to quantitate the relative contribution of thrombus and plaque within the 100 % occlusion that has resulted in the STEMI. Hence some areas may get over apposed and others lesser apposed. Further , the stent -vessel wall interface in all likely hood enclose a layer of clot .This is almost certain during complex primary PCI. One can imagine the sequel if this thrombus layer dissolves later ! (Edentulous stent )
It is surprising , why cardiologists has so far not thought of a self expanding stent which can snugly appose the vessel wall in this setting . The radial strength from the stored potential energy can be used up future use. This is most important in first few days following STEMI , when the coronary arterial lumen can vary depending upon the
Cardiologists deploy a stent based on the morphology on day zero of STEMI .This may be totally irrelevant , since after a few days the lesion may change its morphology , thrombus may migrate , vascular dimension may change. In such a situation* , a self expanding stent can tackle these issues very effectively by constantly adjusting and fine tuning the luminal diameter and the apposition pressure . It does not give any chance for thrombus to form between the vessel wall and stent .
Here is a study that gives fresh insights regarding the role of self expanding stents during STEMI .
Animation
http://www.stentys.com/file_bdd/annexes/1284135580_video_stentys_en.swf
* Logically during primary PCI for STEMI , POBA and thrombus suction may be the best option in many as all stent related complication is instantly eliminated .But it is a battered concept , most of the current day cardiologists would feel guilty to come out of the cath lab without a stent in primary PCI scenario !
Final message
Self expanding stents during primary PCI : Is it a perfect solution for optimal stent apposition ?
It seems so . . . but the track record of current cardiology devices never fulfilled the initial promises !
Dr.S.Venkatesan MD 