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What determines hemodynamic stability in ventricular tachycardia ?

Posted in Cardiology - Electrophysiology -Pacemaker, cardiology- coronary care, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , on October 3, 2008| Leave a Comment »

Ventricular tachycardia is considered as one of the most  dangerous  cardiac arrhythmia .Rather , it is the label  VT  that spreads more  fear than the arrhythmia itself. It is a fact many patients with VT walk into hospital , still  VT will always be a sinister arrhythmia as long as it carries a risk of degenerating into ventricular fibrillation.

What determines hemodynamic stability in VT ?

  • Origin and location of VT
  • The ventricular rate
  • Presence or absence of AV dissociation
  • Impact on mitral inflow pattern
  • Associated left ventricular dysfunction or valvular heart disease.
  • VT in the setting of acute coronary syndrome.(Ischemic VT)
  • Inappropriate drug selection

Origin and location

VTs originating high up in the ventricle( High septal VT,Proximal VTs) have more organised ventricular contraction  and they are more stable.Distal VT  originating  in the myocardium away from the conducting system has chaotic myocyte to myocyte conduction.These are very unstable.

The term fascicular VT is nothing but VTs originating  in the His bundle and it’s branches( Can also be termed Septal VT ).These VTs are also stable and some of them respond well to calcium blockers indicating that they are very close to the AV junction and carry the properties of junctional tachycardia. QRS width gives  a rough estimate about the location of VT. Narrower the VT higher it’s origin.( But remember even in VT ,  qrs can further widen on it’s way downhill !)

LV dysfunction.

This is probably the most important determinant of the outcome in VT. Patients with severe LV dysfunction (EF <30%) fare badly .Hence the land mark concepts from MADIT 1& 2 demanded ICDs in these patients.The most common clinical setting is  dilated cardiomyopathy.SomE of them have bundle branch re entry(BBR).This particular  VT can be stable for many  hours.

Ventricular rate.

Usually VT has a rate between 120-200.Higher the rate of VT more the chances of instability .This rule is also not always true as fascicular VT can be well tolerated at high rates.So location of VT focus  and LV dysfunction usually over rides the impact  of ventricular rate.

Mitral inflow pattern

Proper left ventricular filling is the key to hemodynamic stability in VT. In proximal, septal,fascicular, LVOT VTs doppler studies  suggest (ACC /AHA Type C evidence : Personal observations in CCU during VT) near normal preservation of  bi modal filling of mitral valve inflow.In ischemic myocardial VT  the mitral inflow profile is critically affected . There is no distinctive forward filling was observed .In fact  at rapid rates a short pulsatile MR jets are noted instead.

Associated valvular diseases

It is obvious,  aortic  and mitral valve disorders can aggravate the hemodyanmic instability.

Final message

The clinical behavior of  ventricular tachycardia is widely variable and dependent on multiple factors.

Associated LV dysfunction and  structural heart disease ultimately determine the outcome.

 

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How do you grade pulmonary arterial hypertension ?

Posted in Cardiology - Clinical, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , , , , , , on October 3, 2008| 1 Comment »

                                  Even as cardiology community is preoccupied with systemic hypertension & CAD  ,  pulmonary arterial hypertension(PAH) is a much neglected , still  an important clinical cardiac problem encountered . The irony is self evident , there are half a dozen methods to grade systemic hypertension not even a single stadardised grading available for pulmonary arterial hypertension. The WHO  working group defined pulmonary hypertension  few decades ago and was not clinically graded .The only grading available is based on  the pulmonary vascular biopsy changes (Heath Edwards) 

                                   Currently PAH management has gone through revolutionary changes. There is an urgent  need for grading  this entity .This will facilitate to  diagnose , manage and assess the efficacy of the currently available treatment.

                                Developing countries like ours have a great number of PAH due to rampant rheumatic heart disease.  A simple study was done in  100 patients with PAH .Bulk of the study population had RHD .Few had primary pulmonary  hypertension .Systolic , diastolic, and mean pressure was assessed by doppler echocardiographic analysis of tricuspid regurgitation (TR) and pulmonary regurgitaion(PR) jets. TR jet provided the systolic PA pressure , PR jet provided mean as well as diastolic PA pressure .TR jet was available in all patients. PR jet was available only in 60 patients .Hence the diastolic andmean PA pressure data has been extrapolated in some  and  was plotted in a scatter diagram. Five equal quintiles were divided. Patients in first  and 2nd quintiles were graded 1   and third  and 4th  quintile were  graded 2 ,  5 th  was graded 3 respectively. From this cut off points for  various grades of PAH were identified .The top 3% of patients  with highest PAP were graded as grade 4 and all of them had supra systemic PAH. 

The following grading is suggested for PAH* 

 *This is a preliminary  attempt to grade PAH. This could be applicable mainly in rheumatic heart disese and primary pulmonary hypertension .Further refining of methodology is  required.PAH grading may be little different in congenital left to right shunts.

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Cardinal symptoms in cardiology : Palpitation , some observations

Posted in Cardiology - Clinical, Tutorial in clinical cardiology, tagged , , , , , , , , , , , on October 2, 2008| Leave a Comment »

                        Palpitation is one of the common symptoms for which cardiac patients are referred. Like dyspnea , palpitation can either be a physiological expression of normally beating heart or a  dangerous pathological state of the heart. This makes this symptom unique and warrants careful evaluation.                                                                                                                                                         By definition palpitation  is abnormal  awareness  of ones own heart beat. Heart is a mechanical organ with multiple mobile anatomical structures. There is  constant  blood  flow in multiple directions . Apart from this the heart   has  it’s unique translational, rotational movement . These intrinsic movements combined with proximity to chest wall  generate vibratory  motion  signals .These signals are generally dampened by the encircling pericardial space .The neural signals responsible for  perception  of palpitation is not clear. If the heart hits against the chest wall it is the  somatic nerves from the chest wall that carries the signal. Vibrations generated within the heart chambers, and  and the  valves  are  carried  by the  myocardial and intravascular  sensors.( Autonomic) 

What are causes of palpitation?

       Cardiac

  • All hyperdynamic circulatory states. It may be generated from either  right or left ventricle or both.
  • Regurgitant lesions ( Mainly Mitral and aortic regurgitation)
  • MVPS*
  • Congenital heart disese ( Mainly left to right shunts-ASD/VSD/etc)
  • Apart from this patients  with prosthetic heart valve, and pacemaker patients can feel their heart beats.
  •  Cardiac arrhythmia .Both tachycardia, and bradycardia . Ventricular ectopic beats are the very common cause .( It is often described as missed beat)

* Mitral valve prolapse, a very benign condition, over diagnosed in the last few decades raised considerable anxiety and palpitations for the patients (mainly after the diagnosis ! ).Now the cardiology community has sought to underplay this entity with strict diagnostic criteria.( Thickened mitral leaflet ,presence of MR both must be present to label a patient  as MVPS)

       Non cardiac

  • Physiological
  • Anxiety state
  • Anemia 

What is the relationship between ejection fraction and palpitation?

                                        Generally palpitation indicate a  hyper kinetic state of heart .The commonest cause of palpitation is  anxiety  state .This also happens in hyper dynamic circulations like anemia , fever, thyrotoxicosis, pregnancy etc . In all these situations palpitation indicate increased force of contraction which   generates high dp/dt(Rate of rise of ventricular pressure)  . So  the left ventricularejection fraction is normal or more than normal . So  presence of  palpitation could be an  indirect evidence  of reasonably good LV function.

    “Patients  with dilated cardiomyopathy or CHF rarely feel their heart beat during exertion , instead they have dyspnea  as the LV force of contraction is less”

What is the significance of palpitation that occur during rest ?

                              Palpitation occurring at rest indicate more often a  pathology.It is invariably due to an cardiac arrhytmia  either tachycardia or bradycardia. Intelligent patients can give accurate information about the  regularity of rhythm , any  extra beats or missed beats . Atrial fibrillation, VPDs  could be  diagnosed by history alone in them !

If palpitation  is associated with visible chest pulsation what is the likely diagnosis ?

    If  significant visible pulsation over chest wall  pulsations are seen   in young adults it could simply mean a hyper dynamic circulation and thin chest wall. Pulmonary arterial pulsations is not normally felt in left 2nd inter costal space.If felt one has to rule out shunt lesions like ASD or pulmonary hypertension.
                    “ASD is the commonest cause  of right ventricular  palpitation “  

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Forgotten concepts in cardiology : Amlodipine as an anti anginal drug

Posted in Cardiology - Clinical, cardiology -Therapeutics, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , , , , , , on October 2, 2008| Leave a Comment »

                                                                

 

                         

                            Amlodipine , the most popular anti hypertensive drug  used world wide has an very important action on coronary blood flow.When nifedipine was introduced three decades ago it was  known for it’s powerful anti anginal properties. Subsequently  amlodipine was introduced with almost similar action. But over the years, amlodipine was projected primarily as anti hypertensive drug and gradually many of the physicians are made to believe it is a drug that  should be used only if the blood pressure is high.The fear of reflex tachycardia in few was exaggerated.

                      

                              In fact a cross section of  today’s general physicians were queried  about amlodipine  and none of them acknowledged  using this drug as an anti anginal drug. And few of them went to the extent of withdrawing amlodipine if it was used for the purpose of angina relief !

Why amlodipine’s  anti anginal action is in doldrums ?

The single word answer is unfortunate!   Marketing bias ,coupled with  the fact  that mainstream cardiology texts have ignored this aspect.

Final message

                                    Amlodipine , can still be used as a antianginal drug especially  in a patient who has angina with associated bradycardia  , significant LV dysfunction . Some reserve amlodipine and nifedipine exclusively for vasospastic angina where beta blockers alone are theoretically contraindicated .

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How does squatting help relieve exertional dyspnea in patients with tetrology of Fallot ?

Posted in Cardiology - Clinical, Infrequently asked questions in cardiology (iFAQs), Tutorial in clinical cardiology, tagged , , , , , , , , , , , on October 1, 2008| 2 Comments »

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It is a well known fact squatting is a simple compensatory posture adapted by children with cyanotic heart disease during exertion to get relief from breathlessness. The children with tetrology of Fallot and related conditions have baseline hypoxia due to right to left shunting .This gets aggravated during exertion. Squatting promptly relieves this exercise-induced worsening of dyspnea. The oxygen saturation improves immediately after assumption of squatting posture. The exact mechanism by which squatting relives the dyspnea is not clear.

Apart from squat induced po2 raise there is a fall in the concentration of pco2 and raise in blood Ph that pacify the sensitive respiratory centers,thereby bringing down the tachypnea

Hemodynamics of squatting has two phases

  • Immediately ( First 15 seconds) after squatting there is a sudden drop in venous return.
  • Sustained squatting for 1-2 minutes result in steady increase in venous return, raised systemic vascular resistance.

Both these effects help the children with TOF. The initial trapping of highly desaturated blood in the lower extremity gives a quick relief as soon as the child assumes this posture. In the next 15 seconds or so the systemic vascular resistance increases and bring the aortic after load sufficiently high to divert the blood into the pulmonary artery.

The net effect of squatting is there is a transient or sustained (as long as child squats) increase in pulmonary blood flow and this is made possible by the relative reduction of right to left shunt as the aortic and systemic resistance is raised by this posture.

Other explanations

There is one more possible effect of squatting. By, compressing abdomen (Knee chest) cause a mechanical push on the splanchnic blood pool into the aorta which has high o2 saturation. This is thought to provide immediate relief to brain hypoxia and avoid the vicious respiratory/ hemodynamic cycle

What is the clinical inference from squatting in cyanotic heart disease?

Squatting implies there should be a large VSD, associated with a delicate right to left shunting very much dependent on the degree of pulmonary stenosis or ( any RVOT obstruction) and the systemic vascular resistance.

How common is squatting history in pulmonary atresia with VSD ?

It can occur with collaterals are sparse.The mechanism of relief is slightly different.

The likely mechanism of relief with squatting in Pulmonary Atresia, VSD is two fold.

1. The Initial relief is due to trapping of deoxygenated venous blood in squat posture, which is similar to TOF

2.The sustained benefit is due to raised systemic vascular resistance which favors more flow across MAPCAs from Aorta.

The second one has no authentic reference , but its a hemodynamic plausiblity as there is zero RVOT flow in PA with VSD.

What are the other cyanotic heart diseases in which squatting is reported ?

  • Tricuspid atresia
  • Double outlet right ventricle with pulmonary stenosis
  • Any combination of large VSD and RVOT obstruction
  • Rarely in Eisenmenger syndrome*10%)

*Mechanism of squatting episodes in Eisenmenger is tough to explain. But, it does give relief. The most plausible mechanism is the raise in SVR with squatting tilts temporarily a favorable QP/QS as PVR -SVR ratio falls .(Venous return component doesn’t operate here as in squatting of TOF) It should be noted squatting is mainly reported only in VSD Eisenmenger.. ASD/PDA -Eisenmenger is extremely rare or doesn’t occur. This is understandable as Interventricular communication has to be present to shift in QP/QS with a response to a rise in SVR.

Squat equivalents

Assuming a squat position has cultural issues. Grown-up children may avoid these public places. Standing with legs crosse is a common posture. In fact, the mother holding a crying baby in a chest with knees folded promptly prevents a spell . This can be called “squatting by proxy”

*Though squat equivalents do give relief from dyspnea they are given less significance in terms of diagnostic value of TOF

Reference

1.Paul R. Lurie ,Postural effects in tetralogy of Fallot The American Journal of Medicine Volume 15, Issue 3, September 1953, Pages 297-306

2. Warren G. Guntheroth. M.D.Beverly C. Mortan. m.Venous return with knee-chest position and squatting in tetralogy of Fallot American Heart Journal Volume Volume 75, Issue 3, March 1968, Pages 313-318

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What is the mechanism of pericardial rub ?

Posted in Cardiology - Clinical, Tutorial in clinical cardiology, tagged , , , , , , , , , , , , , on September 28, 2008| 6 Comments »

Heart is externally covered by two layers of pericardium .  Pericardial space is formed between parietal and visceral layers of pericardium . It is a narrow space which is normally lubricated with pericardial fluid up to 25ml. When these two tissue surfaces  come into contact ,  pathological  rub takes place.It is heard  whenever the pericardium is inflammed . Pericardial rub is a distinctive but uncommon  clinical sign .

Common clinical conditions

  • Acute pericarditis
  • Uremic pericarditis.
  • Rheumatic pericarditis
  • Post myocardial infarction

Pericardium has two layers .

There are four  possibilities for pericardial rub to take place.

The rub can occur

1.Between the two layers of pericardium

2.Between the visceral pericardium and the epicardial layer of  heart*.

3.Between parietal pericardium and the  chest wall

4.Pericardium can rub with the adjacent pleura( Pleuro pericardial rub )

The second and third mechanisms are very rare.

An update

We have realized one more possibility . Diaphragm forms the floor of the heart on which the hanging heart  rests . Rubbing of pericardium over diaphragmatic surface is a beat to beat affair that lasts the entire life !. In inflammatory states of  diaphragm especially  the contagious  ones from abdomen  , can result in pericardio- diaphragmatic rubs .These rubs are almost impossible to hear clinically.

pericardial effusion rub plural pleuro pericadial

*The anatomic mystery : Is epicardium same as visceral layer of pericardium ?

Some anatomist feel that both are same entities. If that is the case myocardium can never split its relationship with visceral pericardium.But it is also a anatomical fact visceral pericardium engulfs the coronary artery and  are located sub epicardially.

How many components of pericardial rub are clincally heard ?

Pericardial rub  classically has three components. Systolic, mid diastolic, and pressytolic atrial components. Pericardial rubs are typically described as to and fro rub. Systolic component is most consistent. In atrial fibrillation mono component pericardial rub is heard.

Quality

Superficial , scratchy, high pitched ( Can also be low pitched)

Location

Left sternal border , left 2nd or 3rd space  .Best heard in  sitting , leaning forward in inspiration. Many times the rubs are transient and evanescent . Since it has multiple components it may be mistaken for added heart sound like S 3 or S 4.

What is the mechanism of pericardial rub in the immediate post MI phase ?

Presence of pericardial rub post MI indicate a transmural involvement or atleast significant epicardial involvement . Recognition of this is important as presence of pericardial rub increases the risk of rupture  and hemorrhagic effusion if anticoagulants are used.

What is the  relationship between  pericardial effusion and  pericardial rub ?

Generally it is said with the onset of effusion pericardial rub disappear.But this is not necessarily true.

Rubs after contusion chest and fracture ribs can be with the chest wall and may have  no relationship with effusion.

Is pericardial rub a painful condition ?

Pericardial  rub associated with acute inflammatory pathology is severely painful (like a pleuritis).But pericarditis associated with chronic inflammatory conditions are less often generate pain.The exact reason is not known.

What is pleuro pericardial rub ?

This  clinical entity is poorly defined , often taught by veteran professors  in clinical auscultation classes.It can be heard in the mid segment  or diaphragmatic pleuritis with or without pericardial effusion in patients with  atypical pneumonias.

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What is no reflow ? What is the mechanism of no reflow ?

Posted in Cardiology -Interventional -PCI, cardiology- coronary care, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , , , , , , , , , , , , , , , , on September 24, 2008| Leave a Comment »

No reflow is the terminology used primarily in cath labs where, even  after a successful opening and stenting  of a coronary artery the coronary blood flow is not  restored to myocardium . The point to be emphazised here is blood do cross  successfully the site of  the obstruction but fails to enter the muscle segment  to which the coronary artery is supplying. So the paradoxical situation of artery  being open but the  myocardium is closed to receive  blood flow  happens . This is termed as no -reflow.  Actually it is a  misnomer , and  ideally it should be called “no flow” because  normal distal flow  does not  occur (After PCI)  in the first instance  to get interrupted  later on  and be labeled as  no re-flow.  .The only positive effect of PCI in these situation is blood flow would have improved by few centimeters ie till it reaches  but falls short of myocardium . In fact no reflow , can be termed as  glorified and concealed  terminology  for  PCI failure . It needs urgent action . No reflow is also called as myocardial epicardial dissociation.

Mechanism of no reflow.

Curious case of open coronary artery and closed myocardium !

Coronary  microvascular plugging  is mainly  due to thrombus and atheromatous debri , myocardial  edema , microvascular spasm may also contribute.

Where can it occur ?

  • First described in cath lab, especially following primary angioplasty.
  • It can very  well happen following thrombolysis in STEMI.

  • Can occur in venous grafts.

How do you recognise no reflow?

In cath lab it will be self evident from the check angiogram. Some times it is less obvious and may  require, myocardial  blush score, TIMI frame  count, contrast echocardiography, PET scan etc. In post MI a very simple method to recognise this entity could be the observation of persistent ST elevation in ECG .

Treatment.

Extremely difficult. Almost every coronary vasodilator has been tried.(Nitrates, nicorandil, calcium blockers, etc).Success is less than 30%.  High pressure flushing with saline inside the coronary artery is advocated by some.Others believe it’s dangerous to do it. So prevention is the key. Avoid doing PCI in complex, thrombotic lesions. Use thrombus suction device like export catheter(Medtronic). Distal protective devices are double edged devices , useful only in experienced hands.

Unanswered question

What is the size of the particle (thrombotic and atheromatous  debri)  the   coronary microcirculation safely handle and push it into the coronary venous circulation and the coronary sinus for disposal ?

If we can lyse the thrombus into micro particles by some mechanism and make it traverse the coronary circulation this complication of microvascular  plugging can be treated and prevented .

What is the final message ?

  • No reflow is relatively common condition during emergency PCI done for ACS patients
  • More common in complex thrombotic lesions.
  • Can also  occur in STEMI
  • Treatment is often vexing . In fact the treatment of this condition is so difficult , it can be termed  almost synonymously with “Failed PCI” if flow is not restored.
  • Successful treatment of no- reflow  means not momentry restoration of  myocardial flow  by mechanical and pharmacological modalities ,but to maintain sustained myocardial   perfusion. This we realise, as patients who have had a no reflow during  a PCI, do not perform as well in the follow up  .
  • So prevention is the key.

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Why thrombolysis rarely fails in right coronary artery ?

Posted in Cardiology -Interventional -PCI, cardiology- coronary care, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , , , , , , , , , on September 22, 2008| 7 Comments »

Differential response of thrombolysis between left and right coronary system

  • Thrombolysis is the specific treatment for acute myocardial infarction. ( Privileged few , get primary PCI))
  • Failed thrombolysis occurs in significant number of patients ( 30-40%).
  • Persistent ST elevation  120 minutes after thrombolysis is best indicator of failed thrombolysis.
  • It has been a consistent observation  failed  thromolysis  is more frequent in anterior   or LAD myocardial infarction.

In a simple study we have documented  patients  with inferior MI  rarely had persistent ST elevation and thrombolysis  was   successful in vast majority  of  patients  ( Except in few patients associated lateral MI)

 

The mechanism of better thrombolysis in right coronary artery  is simple.The success of thrombolysis , apart from early time window , is directly correlated with pressure head  and the duration of contact between the thrombolytic agent and the thrombus. In right coronary circulation the  blood flow is continuous ,  occurs  both in systole and diastole that facilitates the maximum delivery of the thrombolytic agent . Further there is a favorable  pressure gradient  across RV myocardium  as the transmural occluding pressure across RV is considerably less then LV myocardium.

This paper was presented in the  “Annual cardiological society of India scientific sessions”

at Chennai, Tamil Nadu.India December 2000

Click to down load PPT full presentation

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In which tachycardias electrical cardioversion is ineffective or rather contraindicated ?

Posted in Cardiology - Clinical, cardiology- coronary care, Infrequently asked questions in cardiology (iFAQs), tagged , , , , , , , , , , , , , , , , on September 20, 2008| 4 Comments »

                              Cardioversion with DC shock  offers immediate cure in many of the dangerous ventricular and atrial tachycardias.  It is often  taught ,  any hemodynamically unstable tachycardia  refractory to  medical therapy respond to electrical cardioversion.  One should also  remember electricity is in fact be called  as a drug !  and it should be delivered in proper form and dose. Here it is the paddle size, paddle position and the axis of current flow all are important. Now we have bi phasic currents for better efficacy.

                             While it is true, most of cardiac arrhythmias respond to shock,  there are few which do not respond or respond very transiently.There are few arrhythmias  in which ,DC shock is not only ineffective but may precipitate a ventricular  fibrillation.

                            Generally arrhythmias of reentrant etiology respond well to DC shock were interuption of  electrical circuit by external current is easily possible. In arrhythmia’s of enhanced automaticity ,  and ectopic tachycardia  it is difficult  to extinguish  the tachycardia focus with DC shock .

Arrhythmias where DC shock is not going to work are

A. Mutifocal atrial tachycardia(MAT)

B. Digoxin induced arrhythmias.Patients who are on digoxin,  has  enhanced ventricular  automaticity.These patients if they  get a DC shock will unmask the  ectopic foci.

C. In elderly with atrial fibrillation and sinus node dysfunction it may be dangerous to shock them with out temporary pacing support as sinus node goes for prolonged sleep mode.

D.In electrical storm with VT ,  if more than three shocks are required within a minute,  the VT will most often going to be permanent and the  electrical therapy can be termed as a failure. These patients will require intensive pharmacological management( Including magnesium, bretyllium etc)

E. And finally , sinus tachycardia (whatever the rate)  is an absolute contraindication for DC shock.

 Verapmil is often effective in MAT  but correction of hypoxia and acidosis may be critical.For digoxin induced arrhythmias phenytoin may be tried.

What to do when the DC shock fails?

  • It will be a  tricky situation and one wonder what to do next when the so called  universal antidote for cardiac arrhythmia fails !
  • Cellular internal millieu  is altered  by hypoxia and acidosis .It may prevent the  effectiveness of cardioversion.So try to correct them .
  • Over dirve atrial  pacing  is one option for automatic tachycardia.
  • And now ablation of arrhythmic focus is possible with radio frequency waves  in some of these patients.( Diffiuclt as an emergency procedure)

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How do you identify left atrial enlargement in X ray Chest ?

Posted in Cardiology - Clinical, X ray, tagged , , , , , , , , , , , , , , , , , on September 18, 2008| 1 Comment »

                                       Left atrium is the posterior most chamber of the heart.  It is almost a mid line structure.  The normal size of left atrium is about 4 / 4 cm. Normal left atrial volume is 46ml in men and 38 ml in women .(Atrial volume in a normal adult population by two-dimensional echocardiography Y Wang, Chest, Vol 86, 595-601.)  Left atrium  is not an easy chamber to identify in the  X ray chest as it does not form  the cardiac border.( Except a small circumference of left atrial appendage.(LAA)

Left atrium can enlarge in multiple directions.Generally it dilates in the path of least resistance.

 

  • It is believed left atrial appendage  enlargement occur early .  LAA enlargemnet seen as a fullness beneath the pulmonary artery shadow. It may be the earliest finding of LAE in X ray. ( This may appear as straight left heart border , as in classical  mitral stenosis where MPA is also enlarged). The LAA enlargement is not necessarily in  in proportion  with LAE.
  • LA could  also enlarge posteriorly by pushing the esophagus towards the spine.This is visible only in barium swallow.
  • Then LA can enlarge either to left or right ( Usually towards right) and  reach the right heart border or over shoot it and form the right heart border by itself.This occurs very late in the course.
  • The other direction  LA goes on to enlarge is superiorly. When LA enlarges superiorly it hits on the left main  bronchus and lifts it.This is measured by the widened subcarinal angle which is normally less than 75 degrees.
  • LA can enlarge anteriorly  sometimes , but it is resisted by right ventricle but rarely right ventricle yields to the LA push and produce a left parasternal lift which could be mistaken  for RV enlargement.
  • Inferior enlargement can not happen in a significant way as it is limited by the AV groove and strong fibrous skeleton. 

With the advent of echocardiography X ray assessment of LA is redundant .(Academic value and in fellows training programs).The upper limit of normal LA size is around 4.5cm.

LA enlargement is commonly seen in

  • Rheumatic mitral stenosis, regurgitation. Gross enlargement up to 10 cms are common.
  • Hypertensive heart disese.
  • Cardiomyopathy, especially restrictive where both atria enlarge.

In all these conditions if  atrial fibrillation occurs  LA size increases further.

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