Cardiovascular (2) Flashcards
What is Heart Block?
- Impairment of the atrioventricular (AV) node impulse conduction
- Represented by the interval between P wave and QRS complex
What is first degree Heart Block?
- Prolonged conduction through the AV node
- PR interval > 0.2 seconds
- Asymptomatic first-degree heart block is relatively common and does not need treatment
What is second degree Heart Block (Mobitz type 1- Wenchebach)?
- Progressive prolongation of the PR interval until a dropped beat occurs
- The progressive prolongation of AV node conduction culminating in one atrial impulse failing to be conducted through the AV node
- The cycle then begins again
What is second degree Heart Block (Mobitz type 2)?
- Intermittent or regular failure of conduction through AV node
- PR interval is constant but the P wave is often not followed by a QRS complex
- Also defined by the number of normal conductions per failed or abnormal one (e.g. 2:1 or 3:1)
What is third degree Heart Block?
- Also known as complete heart block
- No relationship between atrial and ventricular contraction ( no association between the P waves and QRS complexes)
- Failure of conduction through the AV node leads to a ventricular contraction generated by a focus of depolarization within the ventricle (ventricular escape)
What is the aetiology of Heart Block?
- Most common cause: MI or ischaemic heart disease
- Infection e.g. rheumatic fever, infective endocarditis
- Drugs e.g. digoxin ,b-blockers, Ca2+ channel blockers
- Metabolic e.g. hyperkalaemia, cholestatic jaundice, hypothermia
- Infiltration of conducting system e.g. sarcoidosis, cardiac neoplasms, amyloidosis
What is the epidemiology of Heart Block?
- The majority of pacemakers implanted annually are for heart block
- First degree heart block is associated with increased risk of AF
What are the features of Heart Block?
- First degree and Mobitz 1: Usually asymptomatic
- Syncope
- Heart failure
- Regular bradycardia (30-50 bpm)
- Wide pulse pressure
- JVP: cannon waves in neck
- Variable intensity of S1
What are the signs of Heart Block on physical examination?
- Often normal
- Complete heart block:
a. Slow large volume pulse
b. JVP may show ‘cannon waves’ - Mobitz type II and third-degree block:
a. Signs of a reduced cardiac output (e.g. hypotension, heart failure)
What are the ECG findings for First degree Heart Block?
Prolonged PR interval (>0.2 s)
What are the ECG findings for Second degree Mobitz 1 (Wenchebach) Heart Block?
- Progressively prolonged PR interval, culminating in a P wave that is not followed by a QRS
- The pattern then begins again
What are the ECG findings for Second degree Mobitz 2 Heart Block?
- Intermittently a P wave is not followed by a QRS
- There may be a regular pattern of P waves not followed by a QRS (e.g. two P waves per QRS, indicating 2:1 block)
What are the ECG findings for Third degree (complete) Heart Block?
No relationship between P waves and QRS complexes
What are the investigations for Heart Block?
- ECG: different findings
- CXR: may show hilar lymphadenopathy, cardiac enlargement, pulmonary oedema
- Bloods:
a. TFTs: hypo or hyperthyroidism
b. Digoxin level: identify cause
c. Cardiac enzymes, troponin: may be elevated - Echocardiogram:
Ventricular dysfunction or hypertrophy, valvular disease, wall-motion abnormalities
What is the management for asymptomatic first-degree AV block or type I second-degree Heart Block?
- No specific treatment is required
- Patients are at low risk for progression to higher-degree AV block
What is the management for symptomatic chronic Heart Block?
- First line: stop all AV-nodal blocking medications: beta-blockers, non-dihydropyridine calcium-channel blockers, and digoxin
- While discontinuing these medicines may improve AV conduction, they are not likely to completely reverse a clinically significant AV block
- If severe: Permanent pacemakers should be considered (recommended in patients with third-degree heart block, advanced Mobitz type II and symptomatic Mobitz type I)
What is the management for acute Heart Block (e.g. secondary to MI)?
If associated with clinical deterioration, IV
Atropine (anti-muscarinic) and consider temporary (external) pacemaker
What are the complications of Heart Block?
- Asystole- cardiac arrest
- Heart failure
- Complications of any pacemaker inserted
What is the prognosis for Heart Block?
Mobitz type II and third-degree block (advanced) usually indicate serious underlying cardiac disease whereas first degree and Mobitz type I have a low risk
What is Hypertension?
- Defined as systolic BP >140mmHg and/or diastolic BP >90mmHg persistently/ measured on three separate occasions or
- A 24 hour blood pressure average reading >= 135/85 mmHg
What is malignant hypertension?
Defined as BP 200/ 130 mmHg
What can hypertension be divided into?
- Primary (around 90-95%):
a. Essential hypertension
b. No single disease causes the rise in BP, associated with ageing - Secondary:
a. A wide variety of endocrine, renal and other causes
What are the different secondary causes of hypertension?
- Renal disease:
a. Glomerulonephritis
b. Chronic pyelonephritis
c. Adult polycystic kidney disease
d. Renal artery stenosis - Endocrine causes:
a. Primary hyperaldosteronism
b. Phaeochromocytoma
c. Cushing’s syndrome
d. Congenital adrenal hyperplasia (11-beta hydroxylase deficiency)
e. Acromegaly - Other:
a. Glucocorticoids
b. NSAIDs
c. Pregnancy
d. Coarctation of the aorta
e. COCP
What are the presenting symptoms of Hypertension?
- Often asymptomatic
- If secondary, symptoms of the cause