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Posts Tagged ‘silent angina’

Angina is the classical clinical counterpart   of  myocardial Ischemia.

True  Ischemia , by electro- physiological rules  must elicit some sort of  ST segment shift .(Usually  ST depression rarely Elevation  )

But  . . .  we know Ischemia and ST depression do not always go together !  Dissociation can occur in both ways.

ST depression without angina is more prevalent  (often referred to as silent ischemia)  , while angina without ST depression is  less common but by no means rare .

We observe both these  phenomenon  during EST.  The  critical issue  here is ,  any pain without ST depression during a EST , the physician is likely to reject it as  non cardiac.

How wise  it is ,  to ignore such chest pain  ?

If a patient  complaints  true  compressive , squeezing  pain  it should be taken as angina  and EST should be  stopped and labelled as positive   even without  ECG changes .

According to the much   famed (De ) theory on ischemic cascade chest pain is supposed to come last. Time and again the rule of ischemic cascade  goes awry in the bed side. Clandestine angina without any ECG evidence be more important clinical entity than we realize.

                                      The argument against this ,  “If you start believing  patient’s  word  more than  ST depression  then the very purpose of EST documentation is lost  !

According to the now  de-famed theory on ischemic cascade ,  chest pain is supposed to come last. Time and again the rule of ischemic cascade  is found to go awry in the bed side .Clandestine angina without any ECG evidence be more important clinical entity than we realize.

Another clinical situation where we  encounter  ST segment  : Angina dissociation is ,  during balloon inflation of PTCA.

Two  explanations can be offered  for Angina in the absence of ECG changes .

1 .Cancellation of ST vectors  due to ischemia of two diagonally opposite areas of ischemia.

2. Electrical  blind spots  in 12 lead ECG. This  is especially common with LCX ischemia  where most of the electrical events are directed to back of the chest.Conventional leads can easily miss .

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Anginal pain is a type of visceral pain.It is carried by type  C  unmylinated  nerve fibres.The perception of angina is a complex process.It is a combination of visceral and cutaneous referral pain.

How often is angina silent in diabetes mellitus ?

Presence of  diabetes per se does not make an angina silent. In fact,  if  one takes 100 patients with diabetes  , if angina occur in them , it is more often  , manifest than silent. So , only few of  the  diabetic patients who develop diabetic autonomic neuropathy fail to have angina.The exact incidence is not known.It could be around 20%.

If angina can be silent in diabteics , can they have anginal equivalents ?

This again is not answered in literature. Among the anginal equivalents , the most common is  dyspnea , which  can occur in diabetics.But now , we know dyspnea also needs thoracic nerve signals  from the intercostal muscle spindle and colgi organs.This can also be impaired in diabetics.

Can silent and mainfest episodes occur in a same  patient  ?

Yes.

Once silent does not mean always silent, and similarly once angina is felt it  does not mean he is going to feel the next episode as well !

This  strongly reminds us medical science  is  much a complex  subject and what we know is very little in pain perception.

How is silent ischmia different from silent angina ?

There is considerable  overlap  between  silent ischemia and silent angina

The questions to be answered are 

Which is silent  ?  Is it the angina or is it the ischemia or both ?

Silent ischemia can occur in any individual ,  this is also called as silent CAD . When  ischemia occurs  but  fails  to generate pain it is silent ischemia .Undiagnosed  CAD in asymptomatic individuals is also called silent ischemia or CAD.In this population  Exercise stress testing detects  CAD which was otherwise silent and masked.These patients may develop angina during EST.

During exercise stress testing many times patient has significant ST depression  more than 2mm but still chest pain may not occur.These episodes may either be silent ischemia or  ngina. Many times the EST is terminated before angina is manifest .( Chest pain is the last to occur in the chain of events following ischemia- Concept of ischemic cascade )

What are the other situations where angina can be silent ?

  • Pain perception  and threshold  level is  high ,  so patient indeed has anginal  signals but fails to feel it .
  • Patients on  antianginal medication , fail to feel the angina.
  • Chronic betablocker therapy can exactly mimic  autonomic neuropathy

Is it a blessing for the patient  to have painless episodes of angina ? 

When their  ischemic colleagues , suffer a lot with chest pain it is tempting to think these diabetic patients  are blessed!

Scientifically , this could be true in at least in  some  especially in a patients  who’s coronary anatomy is known  and devoid of any critical proximal lesions. For example a small PDA  lesion can produce  severe angina  , but may be silent  in diabetic and be comfortable .This lesion is  insignificant other wise * !

It should  also be recalled , pain relief has been an important goal for treatment  of CAD .In olden days,  thoracic sympathectomy was done for angina . In fact ,  even in  CABG  , one of the the  mechanisms  for  angina  relief  is attributed  to cardiac denervation.

Caution: Even a small  episode of ischemia can trigger an electrical event .But it is rare.

 How common is silent infarct (STEMI) in diabetic patients ?

In a simple questionnaire we asked the diabetic patients in our CCU how they felt their pain during MI.Most felt it normally as do other non diabetic .  Diabetes  does not make  all anginal episodes  silent. Severe episodes of ischemia may be painful while less severe episodes may be painless. Diabetic autonomic neuropathy  is a  least recognized and  poorly understood complication of diabetes.Diabetes , involves  the vasanervorum of the autonomic nerves.

 The other mechanisms postulated in diabetic neuropathy are

  • Reduction in neurotrophic growth factors.
  • deficiency of essential fatty acids .
  • Reduced endoneurial blood flow and
  • Nerve hypoxia .

Is diabetic autonomic neuropathy treatable ?

Very difficult problem indeed.Controlling diabetes may partially correct  the neural dysfunction.Many add on neuro vitamins and aminoacids are having a good market !

If you successfully treat diabetic autonomic neuropathy will my patient  start feeling the  hitherto silent episodes of angina ?

We don’t know.Logic would answer ” YES”

What is the ultimate effect of cardiac autonomic neuropathy.

Cardiac denervation.  The manifestations  are

  • Tachycardia, exercise intolerance
  • Orthostatic hypotension

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