VT versus SVT

Features that favour VT are
- QRS > 140 ms
- cannon a waves on JVP (suggest AV dissociation)
- fusion and/or capture beats
- concordance of QRS complexes in chest leads
- dissociated p waves
- history of ischemic heart disease
- RBBB with left axis deviation
- HR >170bpm

2 algorithms are proposed for prediction of VT versus SVT

i) Brugada
- absence of RS complexes in precordial leads
- RS duration of more than 100ms in any precordial leads
- ventriculoatrial dissociation in any of 12 leads
- certain QRS morphologies, such as QR or QS in V6

ii) Vereckei
- presence of an initial R wave in aVR
- width of an inital r or q wave > 40ms in aVR
- notching on the initial downstroke of a predominantly negative QRS complexes in aVR
- ventricular activation-velocity ratio (Vi/Vt) less than or equal to 1

Coeliac disease

- T cell mediated autoimmune disease of small bowel in which prolamine intolerance causes villous atrophy and malabsorption
- a.k.a gluten sensitive enteropathy
- 95% HLA DQ2 and HLA DQ8
- prevalence : 1 in 300-1500 (more common in Irish)
- occurs at any age (peaks in infancy and 50-60)
- presents with steatorrhea, diarrhea, abdominal pain, bloating, aphthous ulcer, weight loss, iron deficiency anemia, osteomalacia, failure to thrive
- associated with dermatitis herpetiformis
- diagnosis: IgA endomysial antibodies , alpha-gliadin antibodies or anti-transglutaminase antibodies (IgG if IgA deficient - 10% of Coeliac disease)
- duodenal/jejunal biopsy (gold standard): subtotal villous atrophy, hypertrophied crypts of Lieberkuhn, increase in intraepithelial lymphocytes (biopsy reverse/improvement with a gluten free diet)
- treatment: lifelong gluten free diet (wheat, barley, rye, oats)
- complications: risk of malignancy (esophageal, gastric, small bowel), anemia, hyposplenism, lactose intolerance, GI T cell lymphoma (suspect if refractory symptom or weight loss)

Scleritis

- associated with RA, Wegener's granulomatosis, SLE, PAN, relapsing polychondritis
- redness of sclera and conjunctiva or dull purple area of inflammation, with severe deep boring pain, photophobia and loss of visual acuity
- scleritis may lead to perforation of eye (scleromalacia perforans)
- treatment: NSAIDs, steroids eye drops or if severe surgery is indicated

Aspergillosis

- caused by A.fumigatus (most common), A.flavus and A.niger
- these fungi are ubiquitous in environment and commonly found on decaying leaves and trees
- human infected by inhalation of spores
- 3 major forms

i) Allergic bronchopulmonary aspergillosis (ABPA)
- commoner among asthmatics with variable airflow obstruction
- Aspergillus grows in the wall of bronchi
- presents with wheeze, cough, fever and malaise, eventually produce proximal bronchiectasis
- type III hypersensitivity reaction
- suspect if asthma is refractory and is associated with fever, cough and grey/black sputum
- eosinophilia and IgE levels extremely high
- serum precipitins and skin prick test both positive
- abnormal chest X ray (transient pulmonary shadow)
- treatment: prednisolone 30mg daily and prolonged course of itraconazole (up to 4 months)

ii) Aspergilloma
- masses of fungal mycelia that grow in pre-existing lung cavities
- hemoptysis is common symptom
- CXR: round lesion with air halo above it
- high serum precipitins (continuing antigenic stimulation), negative skin prick test
- treatment: surgical resection, itraconazole (if unfit for resection), arterial embolisation if life threatening hemoptysis

iii) Invasive aspergillosis
- occurs in immunosuppressed
- presents with acute pneumonia, meningitis or intracerebral abscess, lytic bone lesions, granulomatous lesions in liver
- treatment: IV voriconazole or amphotericin B

Alpha-1 antitrypsin deficiency

- autosomal recessive
- defective gene in chromosome 14
- alpha-1 antitrypsin protein is synthesized by hepatic cells and released into circulation. In lungs, its primary function is to inactivate neutrophil elastase (enzyme released during phagocytosis in alveolus)
- encoded by protease inhibitor (Pi) locus
- most common (90%) allele is M (PiM). Normal is homozygous (PiMM)
- PiZZ have only 15-20% of normal blood alpha-1 antitrypsin level, which is severe
- Heterozygotes (PiMZ, PiMS, PiSZ) have less severe phenotypes
- smoking is the greatest risk factor for development of emphysema in adults with alpha-1 antitrypsin deficiency
- lung compliance increased in emphysema
- majority of patients with clinical liver disease are homozygotes with PiZZ phenotype, which can produce jaundice and liver problems in neonates within few days of birth

Byssinosis

- caused by cotton dust
- symptoms typically start on the first day back at work after a break (Monday sickness) with improvement as the week progresses
- presents with chest tightness, cough and breathlessness
- most likely aetiology is endotoxins from bacteria present in raw cotton causing constriction of airways of the lung
- CXR is normal

X-linked hypophosphataemic rickets

- dominantly inherited (transmitted by affected father to all daughter)
- defect in renal phosphate handling 
- mutation in the PEX or PHEX genes which encode an endopeptidase
- rickets develops in early childhood and is associated with poor growth
- low phosphate, high PTH, high urine phosphate
- treatment: high dose oral phosphate and vitamin D (calcitriol)

Basic respiratory physiology

Carotid artery stenosis

- carotid artery disease accounts for 20% of stroke and TIAs

- 7.5% risk of stroke and death within 30days of endarterectomy

- there is no benefit to treat completely occluded vessel

Management

- Symptomatic patient < 50% stenosis : optimal medical therapy without revascularisation

- Asymptomatic patient < 60% stenosis : optimal medical therapy without revascularisation

- Symptomatic patient >= 50% stenosis : carotid endarterectomy with optimal medical therapy

- Asymptomatic patient >= 60% stenosis with low operative risk : carotid endarterectomy with optimal medical therapy

- Symptomatic patient >=50% stenosis with high operative risk : carotid stenting

- carotid artery stenting is inappropriate for asymptomatic patient with carotid artery stenosis. Possible exception may include patients with acceptable medical risk who present with severe carotid artery stenosis (>= 80%) with high anatomic risk for carotid endarterectomy but with compelling anatomy for stenting

Source: Clinical practice guideline for society of vascular surgery (J Vasc Surg 2008;48:480-6)

   

Progressive multifocal leukoencephalopathy (PML)

-infection of oligodendrocytes by JC virus (a polyomavirus)
- characterised by progressive damage or inflammation of white matter at multiple locations
- occurs almost exclusively in immunosuppressed individuals
- presents with focal neurological deficits such as aphasia, hemiparesis, behavioural changes and cortical blindness.
- MRI: multifocal non enhancing lesions without mass effects
- viral PCR for JC virus
- brain biopsy (asymmetric foci of demyelination and intranuclear inclusion containing JC virus) has sensitivity of 74-92% and specificity of 92-100%
- no effective treatment but progression can be slowed by initiation of antiretroviral therapy