​Pathology - Second Degree Heart Block Type I
Pathophysiology 
Second-degree AV heart block, Type I, sometimes referred to as "Wenckebach periodicity" or "Mobitz I." This disorder is brought on by an irregularity in the heart's AV node, which leaves the ventricles without receiving all of the atrial impulses. The vignette describes the ECG pattern, which is characterized by prolonged PR intervals that continue until no single atrial impulse is passed via the AV node, resulting in a "dropped" ventricular beat. After that, the PR interval "resets," and the cycle is repeated. For the condition to be accurately diagnosed, the atrial rhythm needs to be regular, or alternative atrial disorders need to be taken into account. Most of the time, this illness doesn't cause noticeable symptoms and doesn't need to be treated. In contrast, nonconducted atrial activity occurs in second-degree AV block, Type II (sometimes referred to as "Mobitz II"), in a far less predictable manner (i.e., no PR interval lengthening and resetting). Cardiovascular pacemaker therapy is recommended for the treatment of Type II second-degree AV block since it has the potential to quickly develop into total (third-degree) heart block. When the ventricles and atria beat separately, it is known as complete heart block, and it also requires the use of an implanted cardiac pacemaker.

​Clinical Procedures - Capsule Endoscopy
Indications
• Obscure gastrointestinal bleeding (in patients with negative gastroscopy and ileocolonoscopy), known or suspected small bowel Crohn's disease, assessment of coeliac disease, screening and surveillance for polyps in familial polyposis syndromes.
Contraindications
• Lack of informed consent, intestinal strictures, adhesions, obstruction
• Diverticula or fistulae that may block the passage of capsule endoscope
• Cardiac pacemakers or other implanted electronic devices
• Difficulty in swallowing tablets or known swallowing disorders
• Pregnancy (lack of available safety data)
• D Patients with obstructive symptoms or known or suspected inflammatory bowel disease should have either a small bowel follow-through or a patency capsule (dissolves after 36 hours), with an abdominal radiograph taken 24 hours after ingestion to identify whether capsule is retained within small bowel:
• If retained, capsule endoscopy is not appropriate
• D Capsule retention can occur even in the absence of strictures on barium or MR-enteroclysis study.
Procedure
• The capsule consists of a disposable, wireless, miniature video camera which can be swallowed and passes through the intestine by peristalsis
• Images taken by the capsule are transmitted, via sensors secured to the abdominal wall, to a battery-powered data recorder worn on a belt
• The capsule leaves the stomach within 30 minutes and the patient is allowed to drink after 2 hours and eat after 4 hours
• The external equipment is removed after 8 hours (approximate battery life) by which time the capsule has reached the caecum in 85% of cases
• The capsule is expelled naturally after 24 48 hours in the patient's stool
• Data from the recorder is downloaded onto a computer workstation which allows approximately 50,000 images to be viewed as a video.
Risks
• Capsule retention (may cause partial or complete intestinal obstruction; highest risk in patients with extensive small bowel Crohn's disease, chronic usage of non-steroidal anti inflammatory drugs, abdominal radiation injury, previous major abdominal surgery or small bowel resection)
• Capsule endoscopy may also fail in patients with dysphagia, gastroparesis, and anatomical abnormalities of the gastrointestinal tract.

The external equipment which the patient will wear, consisting of a data-recorder and electrodes. 
Patient Preparation
• Iron supplements: stop taking 1 week prior to procedure
• Constipating agents: stop 4 days before the procedure
• Fasting: patients are fasted for 8-12 hours prior to the procedure and may receive bowel prep (taken day before procedure).
Other Information
• Incomplete examination in 10-25% of cases:
• Presence of dark intestinal contents in distal small bowel may impair visualization of mucosa
• Delayed gastric emptying and small bowel transit can lead to exhaustion of battery life before capsule reaches ileocaecal valve
• Capsules are being developed to screen for esophageal varices and may be more 'guided' in future as the technology develops
• Positive findings on capsule endoscopy may be reachable using either single- or double-balloon enteroscopy or spiral enteroscopy. 

​Clinical Procedures - Esophagogastroduodenoscopy 
Indications
• Diagnostic: haematemesis, dyspepsia (>55 years old), oesophageal and gastric biopsies (?malignancy), duodenal biopsies (?coeliac), surveillance (e.g. Barrett's oesophagus), persistent nausea and vomiting, iron-deficiency anemia, dysphagia
• Therapeutic: treatment of bleeding lesions, variceal banding and sclerotherapy, stricture dilatation, polypectomy, endoscopic mucosal resection, palliative intent (e.g. stent insertion, laser therapy), argon plasma coagulation for suspected vascular lesions.
Contraindications
• Absolute: lack of informed consent, possible perforation, haemodynamic instability, hypoxaemia with respiratory distress, uncooperative patient
•Relative: pharyngeal diverticulum, recent MI or PE.
Procedure
• Endoscopic examination of the mucosa of the esophagus, stomach, and proximal duodenum. Allows direct visualization, mucosal biopsies,
and other therapeutic procedures
• Dentures (if present) are removed
• Patient is given anaesthetic throat spray (lidocaine) ‡ IV sedation (e.g. midazolam)
• Patient lies on the couch in the left lateral position
• Hollow mouthpiece is inserted to protect the patient's teeth and facilitate instrument passage
• Endoscope (9.5-12.5mm diameter, max. 120cm long) is slowly advanced
and swallowed by the patient
• Scope advanced and manipulated by the endoscopist to allow
visualization of the target structures
• Procedure time varies but average 3-15 minutes.
Risks
• Minor throat and abdominal discomfort
• Cardiorespiratory: arrhythmias, MI, respiratory arrest, shock, death
Infection (uncommon, e.g. aspiration pneumonia)
Perforation (around 0.03% with a mortality of 0.001% during diagnostic procedures, higher with therapeutic procedures):
• Overall 2-3% perforation with esophageal dilatation; mortality 1%
• Bleeding (caution with low platelet counts and high INR)
• Medication effects including anaphylactic reactions and oversedation
• Dental trauma.

Patient Preparation
• Fasting: 4 hours prior to the procedure unless in an emergency situation
• Antibiotic prophylaxis: none for OGD. See other topics for comparison.
Other Information
• Dosages of benzodiazepines and opiates should be kept to a minimum
to achieve sedation, with lower doses being prescribed in elderly patients
• The pharynx is sprayed with local anaesthetic spray. There is some evidence that the combination use of local anesthetic spray and IV sedation increases the risk of aspiration pneumonia
• Patients who have had IV sedation should not drive, operate heavy machinery, or drink alcohol for 24 hours afterwards.

​Clinical Procedures - Colonoscopy
Indications
• Diagnostic: gastrointestinal bleeding, iron-deficiency anemia, chronic diarrhoea, lower abdominal symptoms (chronic constipation, lower abdominal pain, bloating), evaluation of known inflammatory bowel disease (IBD), surveillance for cancer (in IBD patients/after colonic polypectomy/ after curative intent resection of colorectal cancer), screening for colorectal
cancer
• Therapeutic: polypectomy (including endoscopic mucosal resection techniques: EMR), angiodysplasia treated with argon plasma coagulation
(APC), decompression of volvulus or pseudo-obstruction, dilatation, or stenting of strictures or malignant colonic obstruction.
Contraindications
• Absolute: lack of informed consent, toxic megacolon, fulminant colitis, colonic perforation
•Relative: acute diverticulitis, symptomatic large abdominal aortic aneurysm, immediately post-op, recent MI or PE, severe coagulopathies:
• Colonoscopy can be performed safely in pregnancy but should be
deferred in most instances unless requiring immediate resolution.
Procedure
Colonoscopy is an endoscopic examination of the mucosal surface from the anal canal to the terminal ileum.
• Patient lies on the couch in the left lateral position with knees bent
• Endoscopist first performs a digital rectal examination
• Sedation (e.g. midazolam) may be given with monitoring of oxygen saturation. IV analgesia (e.g. pethidine) is also given:
• Increasing use of either no sedation (with improved techniques such as 'Scopeguide®') or inhaled nitric oxide
• Lubricated colonoscope (about 12mm wide and 185cm long) is passed rectally. Air is insufflated. Water-jet may also be used via the scope
• Aim is to pass to the terminal ileum
• Duration varies but averages at about 20 minutes.
Risks
• Perforation (0.2-0.4% diagnostic; higher with therapeutic procedures)
• Bleeding (1 in 1000)
• Abdominal distension, medication effects (allergic reactions, nausea vomiting hypotension, respiratory depression)
• Rarities: infection, postpolypectomy coagulation syndrome: (pain, peritoneal irritation, leucocytosis and fever), splenic rupture, small bowel obstruction.

Patient Preparation
• Iron and constipating agents: discontinue iron tablets 7 days and constipating agents 4 days prior to the procedure
• Anticoagulant and antiplatelet therapy: in the case of a planned polypectomy or other therapeutic procedure, refer to BS guidelines on the management of anticoagulant and antiplatelet therapy (www.bsg.
org.uk)
• Antibiotic prophylaxis: none for colonoscopy. See other topics for comparison
• Bowel preparation: the colon must be empty. Protocols vary but usually include prescribing 1 sachet of sodium picosulfate (Picolax®) for the morning and afternoon of the day before procedure.
Other Information
• The introduction of the bowel cancer screening programme has meant that endoscopists need to pass a 'driving test' to demonstrate high-level competency to perform safe screening colonoscopy
•EMR is used for larger or difficult flat polyps. The lesion is lifted by submucosal injection of gelofusin, adrenaline, and dye followed by snare resection. Polyps can then be retrieved by 'Roth' baskets for histological assessment.

​Clinical Procedures - Barium Swallow/Barium Meal
Barium swallows examine the oropharynx, oesophagus, and GO]; barium meals examine the stomach and first part of the duodenum. They are often performed together as described below.
Indications
• Investigation of esophageal and gastric pathology. Indications include dysphagia, odynophagia, dyspepsia, weight loss, anaemia, epigastric mass, partial obstruction
• I Always consider alternatives (e.g. OGD, MRI).
Contraindications
• Absolute: lack of informed consent, complete bowel obstruction, suspected perforation (a water-soluble contrast may be used instead)
• Relative: a large degree of patient cooperation is required so those unable to understand or follow instructions are unsuitable. Also, the patient must be able to stand for the duration of the examination and to lie supine if necessary.
Procedure
The patient drinks barium whilst the esophagus and stomach are imaged fluoroscopically. Usually performed by a radiologist.
• The patient stands in the fluoroscopy machine
• A gas-producing agent is ingested (e.g. Carbex®) and the patient is asked not to belch
• Images are taken as the patient swallows mouthfuls of barium. The patient must be able to hold the liquid in their mouth and swallow on command
• Once views of the esophagus have been obtained, the machine is tilted so the patient is supine. The patient is instructed to roll and tilt as images of the stomach are obtained from several angles:
• This requires a certain degree of patient fitness
• The time taken depends to a degree on how easily the patient follows the commands, although usually lasts 15-20 minutes
• After the procedure, the patient may eat and drink as usual but is advised to open their bowels regularly to avoid barium impaction.
Risks
• Leakage of barium through an unsuspected perforation:
• Intraperitoneal and intramediastinal barium has a significant mortality rate
• Barium impaction (causing large bowel obstruction) or barium appendicitis.

Patient Preparation
• Fasting: nil by mouth for 6 hours before the examination
• Bowel preparation: none required
• Smoking: patients are asked not to smoke for 6 hours before the procedure as this increases gastric motility.
Other Information
• A barium study will prevent a CT examination of the same area for a period of time as intestinal barium creates dense streak artefact.
Water-Soluble Contrast Examinations
• In the case of recent surgery, suspected perforation, or investigation of a leak, water-based iodinated contrast is used instead of barium.
Examples include Gastrografin®, Urografin®, Niopam®, Omnipaque®
• A single-contrast examination is performed (i.e. the gas-producing agent is not given and many of the 'standard' views are not included
• In contrast to the barium examinations, these studies can be carried out on patients who are frail and/or have recently had surgery
• Intraperitoneal or intramediastinal water-soluble contrast does not carry the risks of barium but aspiration of the contrast can result in pulmonary edema and lung fibrosis. Hypersensitivity is also a risk.

​Clinical Procedures - Computed Tomography (CT)
Indications
• Indications are manifold and too numerous to list.
Contraindications
• The standard radiation protection precautions apply. See separate topic
• The patient must be able to lie flat and still for the duration of the scan
• Examinations of the chest usually require the patient to hold their breath.
Technology
• The CT scanner houses an x-ray tube and rows of detectors which spin at 2-3 revolutions per second, creating a force of up to 25g
• As the patient is moved through the machine, spiral data is acquired which is then converted to 'slices' by the software.
Procedure
This depends on the part of the body examined and the indications for the examination.
• If indicated, the patient may be given oral contrast an hour or more before the examination
• The patient lies (usually supine) on the scanner table:
• Head-first for head and neck; feet-first for almost everything else
• 'Scout' views are acquired which are brief swipes across the area of interest. The resultant images are then used by the radiographer to set the parameters for the scan
• Most examinations involve IV iodinated contrast being given:
• This is usually delivered via an IV cannula by an automatic pump-injection device, controlled remotely by the radiographer
• Contrast may be hand-injected immediately before some scans
• Depending on the part of the body examined, the patient may be asked to hold their breath via speakers in the machine. Microphones within the scanner allow the staff in the control room to hear the patient
• The scan itself lasts no more than a couple of minutes. Time taken to transfer the patient onto the scanner and set up the IV injections will vary.
Risks
• IV contrast reactions including anaphylaxis and nephrotoxicity. IV contrast should not be given to patients with renal impairment unless in special circumstances. Check local guidance
• Extravasation of IV contrast (pain, swelling, erythema).

​Clinical Procedures – Magnetic Resonance Imaging (MRI) 
Indications
• Indications are manifold and too numerous to list. 
Contraindications
• As there is no ionizing radiation, radiation precautions do not apply
• D All ferromagnetic materials will be strongly attracted to the scanner creating missiles which may prove extremely dangerous. MRI-safe trolleys, resuscitation equipment, and wheelchairs must be employed
• D Implanted ferromagnetic devices, aneurysm clips, and retained foreign bodies (e.g. shrapnel or metallic fragments in the eyes) will also move towards the scanner potentially causing major injury
• D Although electronic pacemakers are not made of ferromagnetic material, they may be reset' or stop altogether
• A strict questionnaire is employed before anyone (staff or patient) is allowed near the magnet. If in doubt, access is denied
• Magnetic tape and credit cards may be 'wiped by the magnet
• D Many brands of mascara contain ferromagnetic filaments which may heat and cause burns to the eyelids
• D Caution should also be taken with tattoos some contain iron
• The patient must be able to lie flat and still for the duration of the scan.
Most scanners are relatively tight, larger patients may not fit.
Technology
• The MRI scanner houses a very large electromagnet which is always on
• Radiowaves are produced by the machine, which interact with hydrogen atoms in the patient. Radiowaves are, in turn, produced by the interaction with the hydrogen atoms and are detected by the machine which converts the data into images. The scanner has no moving parts
• The suite houses a Faraday cage preventing radiowaves getting in or out.
Procedure
• This depends on indications and the part of the body examined
• The patient lies on the scanner table. 'Coils' may be placed over the body-part of interest
• Most examinations do not involve IV contrast being given. If this is given, contrast containing gadolinium (Gd) is usually used:
• This is usually hand-injected immediately before the scan
• Depending on the part of the body examined, the patient may be asked to hold their breath via speakers in the machine
• The scan itself can last up to 40-50 minutes for some body parts.

Risks
• Nephrogenic systemic fibrosis (NSF): linked to gadolinium exposure in 2006. Symptoms may begin up to 3 months from exposure and may include pain, swelling, erythema, fibrosis of internal organs, and death. Patients with renal impairment are at greatest risk (no cases
recorded in those with GFR >60) and at least 9 hours of haemodialysis is required to remove it from the bloodstream. 
• Metallic artefacts: twisting or movement of artefacts within the body
• Biological effects: the magnetic fields employed may induce voltages within the body. The most common effect is 'magnetophosphenes' or visual flashes seen by the patient as the optic nerve is stimulated.
Stimulation of other nerves and muscles may occur
• Tissue burns may occur if conducting loops (e.g. ECG leads) are in contact with skin
• Temperature: the oscillating voltages create tissue heating. Overall body temperature may rise by 0.3°C
• Noise: may reach up to 95dB. Headphones or earplugs are usually
worn
• Claustrophobia: experienced in up to 10% of patients.

​Clinical Procedures - Ultrasound (USS)
Indications
• Indications are manifold and too numerous to list. See making best use of a department of clinical radiology via www.rcr.ac.uk.
Contraindications
• For some examinations, the patient must be able to cooperate with the operator and a degree of mobility is often required
• Ultrasound becomes increasingly less diagnostic at greater depths.
Images of deeper structures in large individuals are often unobtainable and this should be borne in mind when considering who to refer.
Technology
• The ultrasound probe houses a piezoelectric crystal which both projects and receives high-frequency sound waves. Much like radar, the
'echos' are converted to images by the machine's software
• Ultrasound cannot image through gas and requires a semi-liquid 'gel' between the probe and skin surface for optimum imaging.
Procedure
• This depends on the part of the body examined and the indications for the examination:
• As ultrasound is a dynamic examination, any part of the patient that can be reached by the probe may be examined
• Time taken will vary depending on part of body examined, patient co-operation and complexity of the findings. Most examinations last between 5-20 minutes.
Risks
• There is no published evidence that ultrasound has ever directly caused any harm to a patient:
• The acoustic output of modern machines, however, is much greater than previously used
• Heating: some equipment can produce temperature rises of 4°C in bone. Most equipment in clinical use is unlikely to increase tissue temperature more than the 1.5°C which is considered 'safe
• Non-thermal hazard: ultrasound has been demonstrated to produce tiny gas pockets and bubbles in animal models. Neonatal lung is considered vulnerable to this but there is no evidence that diagnostic ultrasound can cause harm to other tissues
• Machines have a 'mechanical index' (MI) displayed on screen which acts as a guide to the operator.
Patient Preparation
Depends on the indication and body part being examined.
• Abdomen: patients are usually asked to fast for 6 hours prior to the examination. This ensures distension of the gallbladder and prevents the epigastric structures being obscured by overlying bowel gas
• Renal tract/pelvis: a full bladder is usually required. A full bladder creates an 'acoustic window', effectively pushing small bowel aside so that deeper structures (e.g. ovaries) may be seen.

​Clinical Procedures - Bronchoscopy
Indications
• Diagnostic: histology/cytology in suspected lung malignancy, sample mediastinal lymphadenopathy, alveolar lavage (e.g. TB), transbronchial biopsy (e.g. diffuse lung disease)
• Therapeutic: placement of guidewire for local radiotherapy, direct treatment (e.g. diathermy to strictures):
• Placement of endobronchial stents and the removal of foreign bodies are usually accomplished at rigid bronchoscopy under general anaesthetic.
Contraindications
• Absolute: cardiovascular instability, life-threatening arrhythmia, severe hypoxaemia, respiratory failure with hypercapnia (unless intubated/
ventilated):
•Rigid bronchoscopy contraindications: unstable neck, severely ankylosed cervical spine, severely restricted temporomandibular joints
• Relative: uncooperative patient, recent MI, tracheal obstruction, un-correctable coagulopathy:
• Transbronchial biopsy with caution in uraemia, SVCO, pulmonary hypertension (risk of bleeding).
Procedure
Bronchoscopy is an endoscopic examination of the bronchial tree.
• Patient sits on the couch, leaning back comfortably
• Sedation (e.g. midazolam) may be given with monitoring of oxygen saturation. Atropine may also be given to decrease secretions
• Pharynx is anesthetized with aerosolized lidocaine
• Lubricated bronchoscope (about 6mm wide and 60cm long) is passed nasally or orally with use of a bite-block
• Brushings, biopsy or lavage (50-100mL saline) may be performed
• Duration varies but averages at about 20-30 minutes.
Risks
• Bleeding from a biopsy site and transient fever (10-15%)
• Medication effects: respiratory depression, hypotension, arrhythmias
• Topical anaesthesia: laryngospasm, bronchospasm, seizures, arrhythmias
• Minor laryngeal edema or injury with hoarseness, hypoxaemia in patients with compromised gas exchange (1-10%
• Mortality is 1 to 4/10,000 patients
• Transbronchial biopsy: pneumothorax (2-5%), significant haemorrhage (1%); death (12 in 10,000).

Patient Preparation
• Anticoagulant and antiplatelet therapy: stop for 3 days. Clopidogrel should be stopped for 5 days
• Blood tests: check clotting and full blood count
• Spirometry: perform if underlying lung disease
• Fasting: nil by mouth 2 hours before the procedure, no solids
4-6 hours before procedure.
Post-procedure
• Oxygen: supplemental oxygen for up to 1 hour
• Eating/drinking: drink after 1 hour. If no problems, can eat
• Chest radiography: only if dyspnoea or chest pain following biopsy
(10% risk of pneumothorax)
• Driving: if had midazolam or similar, not to drive or operate heavy machinery for the rest of the day.

​Clinical Procedures – Endoscopic Retrograde Cholangiopancreatography ( ERCP) 
Indications
• Diagnostic: largely superseded by safer modalities such as endoscopic ultrasound and MRI/MRCP. Diagnostic indications include sphincter of Oddi dysfunction and primary sclerosing cholangitis
• Therapeutic: endoscopic sphincterotomy (biliary and pancreatic), removal of stones, dilation of strictures (e.g. primary sclerosing cholangitis), stent placement.
Contraindications
• Lack of informed consent, uncooperative patient, recent attack of pancreatitis, recent Ml, history of contrast anaphylaxis, severe cardiopulmonary disease, futility (anticipated short-term survival with no features of sepsis).
Procedure
An ERCP involves the passage of an endoscope into the duodenum. The endoscopist injects contrast medium through the ampulla of Vater via a catheter. Real-time fluoroscopy is used to visualize the pancreas and biliary tree. Selected images are taken.
• Dentures (if present) are removed
• Patient is given anaesthetic throat spray (lidocaine) and sometimes IV sedation/analgesia (e.g. midazolam, pethidine)
• Patient lies on the couch in a modified left lateral ('swimmer's") position with the left arm adducted and the right abducted. The endoscope is inserted as for OGD
• Under x-ray guidance, a polyethylene catheter is inserted into the biliary tree and contrast instilled to outline the pancreatic duct as well as the common bile duct and its tributaries
• Procedure time varies from 30-90 minutes.
Risks
• Pancreatitis (2-9% of procedures of which 10% of cases are mild-moderate). Serum amylase is temporarily raised in 70%
• Infection (ascending cholangitis, acute cholecystitis, infected pancreatic pseudocyst, liver abscess, endocarditis
• Bleeding, perforation of the oesophagus, duodenum, bile ducts
• Failure of gallstone retrieval
• Prolonged pancreatic stenting associated with stent occlusion, pancreatic duct obstruction, pseudocyst formation
• Basket impaction around a large gallstone (may require surgery).

Patient Preparation
• Blood tests: liver enzymes, platelets and clotting are checked prior to the procedure.
• Nil by mouth: 4 hours except in the case of an emergency.
• Antibiotic prophylaxis: recommended for:
• Patients in whom biliary decompression is unlikely to be achieved at a single procedure (e.g. dilatation of dominant stricture in multifocal sclerosing cholangitis or hilar cholangiocarcinoma)
• Consider also in patients with severe neutropenia (<0.5 × 109/L) and/ or profound immunocompromise.
Other Information
• © I sedation and analgesia is usually administered and the back of the throat is sprayed with local anaesthetic
• Hilar biliary obstruction demonstrated on MR or CT imaging may be more successfully stented using percutaneous transhepatic cholangiography (PTC) than ERCP
• Equipment allowing direct cholangioscopy (with the potential for sampling lesions) is becoming more widely available.