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Posts Tagged ‘Tachycardia’

Ischemic ventricular tachycardia is a  too well recognised clinical  entity  . But , ischemia triggered atrial arrhythmias are less often encountered .

Does that mean , atria are relatively protected from the effects of ischemia ?

Not really  . . .  It  is possible  it may not be  that rare ,  as we think .

And then ,  the semantics play  a major  role !

Atrial fibrillation  is the commonest supra ventricular  arrhythmia  in human ,  we also know CAD is the leading cause of the AF apart from HT & Cardiomyopathy . So technically , ischemic SVT  is  more common than Ischemic VT ,but we do not call it so !

If we analyse the triggers for AF it is more often hypoxia  (than ischemia )  . . .yes there is huge difference between the two .In the ventricles it is more often ischemia that  trigger a VT.

Atrium is very sensitive to systemic  oxygen saturations especially in elderly and COPD patients. This is the reason we get many of the complex atrial arrhythmias in hypoxic situations ( Ectopic atrial, Multi focal atrial , etc) .These arrhythmias are difficult to control unless oxygen saturation is corrected. While  many of AF episodes are transient and disappear after correction of hypoxia.

If the ventricle also  responds with fibrillation  at times of systemic  hypoxia ,  one can  imagine the disastrous consequence ! God is kind enough , systemic hypoxia per se  rarely trigger a VF ,  though  it can maintain a VT which was initiated by some other mechanism.

So what are the causes of  narrow qrs tachycardia in the coronary setting

Apart from AF ,  Ischemic SVT  can occur in the following situations

  • STEMI -RVMI
  • Atrial infarction -Focal AT -Atrial flutter /AF
  • Post Pericarditis
  • Refractory , ischemic JT (Junctional tacycardia ) in elderly , perioperative , hypoxic patients

*Atrial arrhythmias are very rare during unstable angina for some unknown reasons . Atrial scar induced ischemic focal AT is underdiagnosed.

** Never  diagnose AVNRT /AVRT in a patient   who has an ACS. It is likely you will be 99.9% wrong.

*** Preexcited AVRTS are very rare in elderly CAD patients even in those with a history of SVT  .This is because as the age advances the accessory pathways undergo degeneration either by ischemia or  the wear and tear  and get self ablated .

Many times the associated , HT and diabetes may contribute to the arrhythmia.

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                        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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Aberrant cardiac conduction can occur in any of the specialized cardiac conduction tissues. Rate dependent aberrancy is the most common cause of aberrant conduction.

Generally it is thought only supra ventricular impulses can undergo aberrant conduction. But it is not always true.

Many of the ventricular tachycardia which  have inherently wide QRS complex can further widen their QRS width when it conducts fast down stream.This is especially true  in many of the septal VTs and fascicular VT  which  are falsely diagnosed as myocardial VT. These proximal VTs which other wise would have been a narrow QRS VT are converted into wide QRS VT by functional aberration .

Message :

Don’t always think SVT only has a potential to undergo with aberrancy

The VTs also can  behave similarly.

 

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