post 1 STABLE ANGINA PECTORIS

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                                        STABLE ANGINA PECTORIS

Angina is chest pain due to poor blood flow through the coronaries.

Ischemia is enough to cause symptoms but no necrosis

Physical exertion is the most common cause of anginal pain

Severely narrowed coronaries may allow enough blood to reach the myocardium, when O2 demand is low(as in rest).But with exertion  myocardial O2 demand  increases causing angina.

In Stable angina there is no history to suggest increase in severity or frequency of anginal chest pain. And stable anginal attacks are usually predictable, are of short duration;<5min)

 as a rule are relieved promptly by rest.

“Stable angina” shows stability in frequency and severity of pain, and is predictable-during or after physical exercise or emotional stress

Patho physiologically “stable” atherosclerotic plaque of coronary vessel is the cause.)             .

Figure27.2. 1 FIXED CORONARY OBSTRUCTION IN STABLE ANGINA

Precipitating factors

                        Exertion, emotion, exposure to very hot/cold climate, heavy meals and smoking

CAUSES: of Angina Pectoris

1.      most common cause -Coronary atheroma

2.      Other causes

       Aortic valve disease, Aortitis.

Polyarteritis, connective tissue disorders.

         3.   Hypertrophic cardiomyopathy  

         4.   Without any demonstrable lesion –syndrome X

PATHO GENESIS: fig 27.2.1

A.     Defective Supply:

Reduced coronary blood flow, increased coronary vascular resistance.

Lowered O2 carrying capacity -anemia

B. Increased demand:

E.g. increased heart rate, myocardial contractility and wall stress

(which increase in exercise, HT, LV dilatation)

Coronary flow reserve normally increases fourfold in exercise;

In angina –flow reserve is reduced by structural stenosis or spasm.

Some patients have variable effort tolerance called phenomenon of Variable threshold angina, because of dynamic endothelial dysfunction.

CLINICAL FEATURES OF ANGINA PECTORIS

 Diagnosis: History is most important; Diagnosis is only by history.

Typical history-

o   Central chest pain brought on by exertion and relieved by rest or nitrates.

o   Rest relieves pain in a matter of 5min

o   Pain described as squeezing, pressing /tightness in chest

o   Sometimes like indigestion, sometimes indescribable

o   May be associated with nausea, fatigue, dyspnea, sweating, and giddiness.

o   Pain radiates ‘like fountain’ from precardium

 Most commonly radiates to left arm /wrist /hand – inner aspect

 Less commonly to right arm /to neck /jaw /tooth/ back /epigastrium.

 May occur in any of these sites without central chest pain

 Precipitated by - heavy meal /, cold weather /walking up hill/carrying heavy 

 Bags/climbing steep stairs.

(Peripheral vasoconstriction, increased oxygen demand)

o   Breathlessness sometimes is a prominent feature of angina.

o   Anginal equivalents: Dyspnea, palpitation and   giddiness, fatigue, severe weakness on walking.

o   Silent ischemia: Without any anginal symptoms, ischemia may be silent.

                                               

Variants of Angina:

2 main types

Stable angina: vide supra

Unstable angina: Angina at rest and it is accelerated angina (refer chapter on unstable angina)

Other variants

Prinzmetal’s angina – occurs due to occlusive coronary arterial spasm 

               with; “abnormal over reaction to vaso constrictive agents”

 Occurs at rest typically in the early morning hours.

Transient ST Elevation on ECG-is hall mark

Complication; in prolonged attacks-vent. Arrhythmia, syncope, MI

Start –up angina – pain comes on the start of walking but does not

return on continued effort.

Decubitus angina – pain when lying flat ;(áin venous return provokes pain)

Nocturnal angina - awakened by pain in the night

Key message in cases of atypical angina

Such patients should be referred for Stress ECG and are often found to have IHD.

PHYSICAL EXAMINATION: IN ANGINA PECTORIS

   Often negative. But physician must not fail to search for:

o   signs of important risk factors: - e.g. nicotine stain, hypertension, hyperlipedemia (tendon xanthoma, arcus lipidis, thickening of achilis tendon) diabetes, myxedema

o   Contributory diseases:- obesity,  anemia, thyrotoxicosis,  aortic valve diseases/MVPS

o   Left ventricular dysfunction: cardiomegaly, gallop rhythm, basal crackles, raised JVP.

o   Generalized arterial disease: - e.g. carotid bruit, peripheral vascular disease.

DIFFERENTIAL DIAGNOSIS:

Musculoskeletal pain:  aggravated by specific movements like bending, turning, stretching; not by walking.

Background pain persists at rest. In addition chest wall tenderness may be present.

Pericardial pain: provoked by changes in posture and  deep inspiration, sharp.

Oesophageal pain; has burning nature and relieved by antacids ,PPI

Oesophageal spasm: different type of pain, can’t easily differentiate from                                

  Variant angina.

INVESTIGATIONS

I. Resting ECG:

♣Normal mostly; A normal ECG does not exclude angina

♣In some – non specific changes like T wave flattening /inversion

♣May show previous myocardial infarction        

 ♣Definite sign of ischemia are – ST ↓ or ↑ with or without T ↓ - at the time of   symptoms

Remember: ECG does not decide the type of angina including unstable angina: deciding factor is only the history

II. Exercise ECG. /Stress test

Used to confirm or refute a diagnosis of ischemia, to assess severity and diagnose high risk.

Procedure Patient is made to exercise at increasing level of effort on a stationary treadmill or bicycle and 12 lead ECG monitoring done.

BP and general condition also monitored along with.

Signs of ischemia are –ST segment depression of 1mm or more (planar or down sloping) or elevation, arrhythmias, fall of BP.

Caution: If severe chest pain or/ fall of BP /arrhythmia/severe STdepression or elevation develops, resuscitation facilities must be available.

o   False positive results:-in digoxin therapy /, LVH/LBBB/WPW syndrome.           

o   Predictive accuracy of test: less in women.

Principle involved in exercise ECG: When the heart is working hard and beating fast it needs more blood and O₂, Plaque narrowed coronaries cannot supply enough O₂ rich blood in this situation

Other forms of Stress testing:

Stress test can be combined with an imaging modality, which helps to visualize the - ischemic myocardium thus increasing its specificity

Indication1. in those unable to exercise, 2.equivocal stress test results

 Predictable accuracy; higher than in stress test

1. Myocardial perfusion scanning:

Technique: After intravenous administration trace radioactive isotope like Thallium 201/Tc99,

   using a gamma camera, scan of the myocardium is performed in  2 conditions A)At rest

B) After exercise. The gamma camera images the distribution of the radioactive material in the myocardium. If there were to be any differences in the myocardial blood flow, the

-distribution of the tracer will be non homogeneous.

In resting image: Ischemic myocardium appears normal but in stress image -is under perfused

   appearing as a cold spot.

Scarred myocardium which receives no blood flow appears as cold spot on resting and stress images   

Thallium; is analogue of “K”: accumulates in viable perfused myocardium   

o   At a time when enzyme levels have not raised perfusion images can be abnormal                 

.

Tests that can be done in conjunction:

isotope scanning can be done along with ETT or pharmacological stress like controlled infusion of dobutamine.

echo/radionuclide blood pool scanning: - done to measure ventricular function

.

2. Pharmacological Stress test: For patients who are unable to exercise:

Controlled infusion of Dobutamine is administered. This increases heart rate and myocardial contractility thus simulating the effects of exercise. Dypiridamole or adenosine may be used instead of dobutamine.

3. Stress Echocardiogram:

This stress test is combined with Echo imaging of the heart.

In ischemic or scarred myocardium it shows wall motion or functional abnormality.

Has same predictive accuracy as SPECT.In addition it is convenient, relatively cheaper,

and helps in valvular evaluation also. Physiologically wall motion changes precede ECG changes.

Results of this test help in deciding the severity of the coronary stenosis

III. Non Invasive Investigations:

A) Routine: X-ray chest

B) Echocardiogrphy:

 Detects regional /global systolic dysfunction, valvular lesion, HOCM.

C) Electron Beam Computed Tomography:

 Evaluates calcium content in the coronary arteries. And predicts MI in asymptomatic; sensitive but not specific test; not recommended as a routine tool for investigation.

D) Multi slice detector computed tomography; (MDCT):

An alternative to invasive coronary angiography.

64 slice multi detector computed topography: can be used to rule out acute coronary syndrome in patients with chest pain; quickly and accurately excludes the presence of IHD

E) MRI

F) PET scanning

.Lab tests:

Complete hemogram to exclude anemia, Lipid profile to identify hyperlipedemia, serum creatinine to identify renal impairment, fasting blood glucose to identify DM, Thyroid function test to exclude thyroid disease if there is clinical suspicion

What is the role of above investigations in Angina pectoris?

 In difficult cases Tread mill test, nuclear cardiac studies and Echo will confirm the diagnosis of angina.

If these tests show gross abnormality patient should undergo coronary angiography to decide if he needs angioplasty or Bypass surgery

Remember –in patient with unstable angina stress test is ‘contra indicated’.

IV. INVASIVE TESTS                                                                                                       

CORONARY ARTERIOGRAPHY:

 Gives direct evidence; also help to study extent and nature of ischemia /infarct;

Indication:

¬Done usually to plan coronary by pass grafting or angioplasty.

¬Extent and severity of the disease is assessable.

¬Rarely done as diagnostic test; done only if non-invasive tests don’t diagnose pain.

RISK STRATIFICATION IN ANGINA:

Low risk: predictable exertional angina, good effort tolerance, ischemia only at high work load (ETT), single vessel or minor 2vessel disease,

 High risk: Unstable angina, Post infarct angina,

Poor effort tolerance, ischemia at low workload, left main or 3vessel disease, poor LV dysfunction

Patient may fall between these 2 groups

Computer programmes –

Cardiac Risk Assessor is available for calculating risk.

Also coronary risk charts are available.

Natural History of Angina: types of progress

1.Patient  may go on getting anginal pain for many years without getting myocardial infarction and vice versa i.e. patient getting MI without ever having suffered from angina

2. Over the years patient can go on to unstable angina ie angina at rest or when losing temper.

3. If the pain lasts for more than a few minutes and is accompanied by profuse sweating- diagnose Myocardial infarction.

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