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Posts Tagged ‘bradycardia’

Bradycardia is a common cardiac arhythmia. Sinus bradycardia  is  often considered an arrhythmia from a disciplined heart. It denotes high vagal tone .  A  heart rate  of  40 , some times even 35 is well tolerated . But bradycardia due to heart blocks are dangerous.

Sinus bradycardia can not get lower than 30/mt or so , as invariably either the  junction or the  ventricle , escapes with its own rhythm. Near syncope, dizziness , giddiness followed by  syncope  occur as the  heart rate  slows progressively below this level .It is often taught humans can not survive  when the heart  rate  goes below 10/mt .

Case report :

Here is middle-aged man who  presented  with a history of  recurrent syncope over a period of  3 days . He has no  history of CAD.

As he entered  the ER, this ECG was recorded.

At this pint of time  , when the ECG was recorded,  he was  conscious and talking ,  only to complain  of  little dizziness. After seeing this ECG , he was immediately put on a  temporary pacemaker.

Note : The ECG shows a single qrs complex per tracing of 10  sec duration .Ie HR of 6 /mt.One qrs complex for 50 large squares !  .Divide  300/50 and HR is 6 . Note also the p waves fire at 150/mt due to atropine effect .

The procedure  took 15 minutes to perform  , he was comfortable  and was administered atropine , and isoprenaline *, which increased his heart rate  from  6/mt to 10/mt .

Later he went on to receive a permanent pacemaker a week later.

* Temporary trans-cutaneous pacing using paddle stickers  is  an another  modality available in such situations where trans-venous pacing is  likely to be delayed  .

Message from this case

Cardiology’s  ultimate  moment of glory and truth  is experienced  when a  life  is saved with  a pacemaker.

Extreme bardycardias are  often  fatal , but here is a patient with  dangerously  low heart rate , still not resulting in asystole  or brady induced VT/VF . We had adequate  time to plan a strategy . Severe bradycardias  need not result in cardiac  arrest always.  Some hearts  have amazing capacity   and their  fighting spirit   amazes  us !  .It should be noted that , the above example may be  an exception than a rule .

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atropine leafsAtropine ,  the extract from the  Belladona  plant  is an important cardiovascular  drug. It’s  presence is vital  in every crash carts .  This  unassuming molecule  probably has   saved more cardiac lifes than any other drug . It provides immediate  remedy for many of the bradycardias .It  works like a magic.  The physician buys  time with this molecule  and  proceed  on to resuscitate or  plan other interventional  procedures. It is most powerful antiarrhytmic agent known .It is an irony , many of  the standard cardiac texts do not even mention this while discussing anti arrhythmic agents .

In  this  era of  hyped  cardiac  care   , the  sartans ,  2b3a inhitors   , the fondaparinux’s  making merry !  we  have no spare time  to realise  ,   more  cardiac  deaths  have been prevented by atropine  than  all these   drugs    put together.  It is still working like a bull  across the coronary care units and cath lab world over. While  many mediocre  drugs  enjoy a  big  bash  time for  possibly  saving   few occasional  lives   , the atropine  like drugs never get the due recognition among cardiac literature for the simple reason ,  it being a  cheap  generic drug.This drug is available  for few  rupees , no marketing no advertisements, no celebrations.

Mechanism of action

The  biochemical  mediator :  Acetyl choline

Site of action :     It blocks the M2 (Muscaranic receptors) .

We will confine to the cardiovascular  actions.

  • SA nodal acceleration
  • AV nodal accelerated conduction

Effect on ECG

Sinus tachycardia

Short PR interval

Life saving situations in cath labs  in CCU.

Vagus  nerve richly innervate the heart and blood vessels . Acute coronary syndromes   especially involving the infero posterior territory  raises the vagal tone  , and can  in severe bradycardia and hypotension.  In cath labs , as we  manipulate  cardiac  structures with wires and  catheters  there is always  a potential to elicit the vascular reflex .It can occur  any where between the  access point , femoral or radial  artery to coronary arteries .

Further ,  whenever the  pain  intensity is more , the  central pain integrating  centre in  brain stem  and thalamus has a spill over effect into the vagal nucleus .

What happens if a vaso vagal reaction is left untreated ?

We have often  made  the term “vaso vagal  reaction” appear as an  innocuous  entity. The main reason for this perception is   due to the common occurrence of  “vaso vagal  syncopewhich  is largely a benign entity in the general population .This fact  has sensitised our brains . One should distinctly realise the vaso vagal syncope that occurs in  healthy people standing  in erect posture ,  from  vagal reactions that  occurs in  lying patient with a diseased heart  in a  cath  lab  or CCU.In the classical vaso vagal syncope , assuming the recumbent posture is the treatment and it  counters the hemodyanmic imbalance .No drug is required here. So the common vagal syncope can never be compared with potentially dangerous  vagal reflex that occur in CCUs and cath labs. If not recognised earlier and  immediately countered  it can lead on to asystole and death .Many of  the delayed deaths post PCI during sheath removal or an episode of vomiting are directly related to this.

atropine

Atropine is the Savior here . Can you imagine a  world without atropine .

The other reason we had always considered vaso vagal   reactions lightly is that the poor atropine is always available  in the side selfs and it acts   rapidly  and promptly with almost  100 % success  reversing the vagal action  in less than  60 seconds .

How often we here  this  “Oh it’s a brady . . . push  2cc atropine . . .  given sir, the rate has picked up . . .”

If only atropine has a failure rate of say  50%    we  would have  realised the full impact of   vaso vagal shocks (See … how we struggle with No reflow   with no effective drug available !)

Is there any other alternative  treatment  for vaso vagal shock other  than atropine ?

No.   (I guess so . . .Readers may correct me )

Other uses of atropine in cardiac practice

  • During stress testing along with dobutamine  to  increase the heart rate.
  • It can be used to differentiate AV blocks the two types of 2nd degree AV block. The mobitz type 2 worsens while type one accelerates.

Non cardiac uses.

Ophthalmology, pre anesthetic medication, bronchial asthma, various poisoning.

What is the future for this molecule ?

Remain bright .  But only very  few companies make this molecule.  It is a drug that can not  fill the cash boxes but  it is a drug to keep the human heart running at times of crises  . The only  threat to this drug  is  the  possibility of it being replaced with a  modified patented  version of this great  molecule  !

Final message

The evolution of medicine is based on strong foundations  put upon by clinical acumen   by great medical men of  past generation. Atropine was developed by such people   and it has withstood the test of time. This drug  probably  has saved ( and  continue to  save)  many  lives  than any  other drug  in cardiology . It should be recalled ,  another great cardiac drug   called digoxin  has almost succumbed to modern medical  forces  .Let us  keep developing   new molecules  ,  we shall also pay  tributes  to some of   the  unassuming drugs in cardiology .

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ecg-ventriculophasic-21

Ventriculophasic sinus arrhythmia is a non-respiratory sinus arrhythmia seen in complete AV block.

The PP interval enclosing a QRS complex is shorter than a PP interval not enclosing a QRS.

The Mechanism 

ecg-ventriculophasic-sinus-arrhytmia1

The proposed mechanism is the  increased blood flow into the SA node artery  during ventricular systole  stimulating it to produce an early pacemaker activity and thus shortening the sinus cycle length.

Clinical significance : None for the patient  Academic purpose for the students

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sinus-node

 

Sinus node  as the pacemaker , orchestrates the rhythm of life . It has  to fire for the entire life time of  a person.It  can not afford to take any rest ! But it can pause a little bit , of course that pause  could  be less  than 15% of it’s basic sinus length. This variation of sinus  cycle length is called sinus arrhythmia.This is physiological. When it exceeds 15 % of the previous sinus cycle it is referred to as sinus pause.

 Have a look at this ECG

sinus-pause-2

 

What follows a long pause ?

By strict terms  of definition a sinus   pause should be followed by  a delayed , next sinus  beat only. A  sinus pause  , many times  is followed  by   JPD – Junctional escape beat.This situation should be ideally  referred to sinus arrest as the sinus node is taking too much of rest and it is not able to wake up from the slumber and it needs assistance form the junctional pace maker.

So even though sinus pause and sinus arrest is used many times interchangeably, it should be avoided. 

What are the electrophysiological mechanisms of sinus pause ?

  • Simple sinus bradycardia . The commonest  mechanism is  the  increased vagal tone. This occurs more often in young athletes. Eventhough increased vagal tone  conveys   a innocuous meaning , at times  this can also be symptomatic  and require intervention.
  • Sinus node exit block.
  • First degree, second degree, complete SA block can occur as in AV node.

First degree SA block can not be diagnosed by surface ECG. Third degree SA block is same as sinus arrest and subsidiary pacemaker will function in these patients.  Second degree SA block is usually diagnosed when the sinus pause is in the multiples of resting sinus cycles. If the pauses are not in exact multiples  sinus arrest is diagnosed. All these arrhythmia’s are collectively called sinus node dysfunction(SND)

How do you manage these patients?

Sinus node disorders can occur in number of systemic diseases*. It  needs to be  ruled out.

  • Infiltrating diseases like amyloidosis, hypothyroid states can result in SND.
  • Drug induced SND like beta blocker and calcium blockers are fairly common and should be excluded
  • Some congenital heart disease (SVC ASD) can involve sinus node.
  • Ischemic SA node disease is rare but can occur  following  infero posterior  myocardial infarction
  • Sinus node disorders are  very often related to degenerative atrial diseases associated with HT, cardiomyopathy etc

*The list is not exhaustive

A very important association is noted  with atrial fibrillation as  a part of tachy brady syndrome .The link between SND and AF  is obvious as   atrial pathology is the common denominator in both ! This will be discussed later.

When is a  pause  significant ?

Any pause that is producing significant symptoms is significant.This depends upon the overall  hemodynamic compensation of the patient.Young, and fit can even tolerate three second pause without symptoms.Underlying heart disease makes even a smaller pause symptomatic.But generally a 3  second or more  pause is almost always pathological .Pauses can be up to  5  seconds (  a 5 second pause actually means a  heart rate of 12/mt , obviously it can not go on for a minute, a patient will develop a syncope). A 3 second pause  corresponds to 20/minute.

How will you evaluate a patient with sinus pause ?

There are sophisticated electrophysiological studies (EP) available like sinus node ECG ,sinus node function studies like sinus node recovery time, activation time etc. But these are generally of  academic interest.

If a patient is symptomatic  (syncope) because of bradycardia  he requires a pacemaker and  EP study is redundant . Similarly , if  he is totally asymptomatic in spite of pauses , again  EP study is  not  indicated.

Only for patients  in the  grey zone,   further studies are indicated .This would include a extended holter, loop recorders, event monitors etc.

Another important issue to consider  is , before putting a pacemaker   patient”s   symptom  must be correlated  with their arrhythmia.

What is  the overlap  between sinus node dysfunction and neuro cardiogenic syncope ?

SND  can occur as an overlapping syndrome with neurocardiogenic syncope.(NCS ).NCS is also a very common cause of syncope .In NCS  there are two limbs .Cardio inhibitory and vasodepressive. The cardio inhibitory form can exactly mimic an SND. In a given patient  it is very difficult to pinpoint which of this limb is dominant.Head up tilt test(HUT)  might help in few.  If a patent’s symptoms are due to inappropriate vasodilatation pace maker may not reduce the symptom of dizziness or syncope.

Management

  • There is no ideal  medical therapy* available as on date
  • Withholding all drugs which might aggravate bradycardia is of paramount importance.
  • Pace maker is the specific treatment in all symptomatic patients.

*Aminophyline tablet may be useful in some patients .It acts by antagonising adnosine receptors in SA node.Other drugs which can incrase the heart rate in the short term include  Orcipranaline(Beta 2 stimulant /Alupent ) Probantheline(M 1 blocker)

The key issue is to avoid unnecessary pacemaker implants in patients who have insignificant pause.

 Which pacemaker is ideal in SND ?

pacemaker

                                                              The need for dual or single chamber pacemker will be taken by the electrophysiologist .Atrial based pacemaker (AAI)  is preferred as it gives physiological pacing .But a simple ventricle based VVI pace maker is good enough in vast majority of patients. This takes care of   future risk of AV block also. DDD pace maker is the most physiological pacemaker and it is supposed to provide better quality of life. But it has an issue of insertion and  maintenance of  two leads, multi parameters to be programmed.It should switch to appropriate modes  at different times.(Like VVI mode during atrial fibrillation etc).Trouble shooting needs expertise , while  VVI is simple,  safe , and just effective as well .(In this turbulent world, quality of life is a  too trivial an issue  to be determined by a DDD  maker)

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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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