cardiac pacing and bradycardia, cardiac tamponade Flashcards
differnce between left and right ventricular pacing and patterns shown
In right ventricular pacing the QRS morphology is similar to left bundle branch block.
In left ventricular pacing the QRS morphology is similar to right bundle branch block.
In dual chamber pacing there may be features of atrial pacing, ventricular pacing, or both.
The gentleman’s ECG above shows a sinus pause or sinus arrest of longer than 3 seconds. This is an indication for
the implantation of a permanent pacemaker. The pacemaker once implanted will be set to pace the heart at a minimum base rate to avoid this happening again and the patient dying in their sleep or having further pre-syncopal episodes
A 66-year-old male has an unprovoked ventricular fibrillation cardiac arrest in hospital. After successful resuscitation and recovery, an implantable cardiac defibrillator is inserted.
How long must he wait until he can drive a car again?
6 months
Mobitz type II block
Complete heart block + broad QRS
Recent asystole
Ventricular pause >3 seconds
If any of these features are present in a patient with bradycardia and no adverse features then
then atropine should also be administered. If there is an inadequate response to atropine, alternative drugs include isoprenaline, adrenaline, aminophylline, dopamine, glucagon (in beta blocker/ calcium channel blocker overdose) or glycopyrrolate
if acute bradycardia what should you do - if due to CCB or BB overdose
give glucagon
how does atropine work
Atropine is an anticholinergic; it blocks the effects of the parasympathetic nervous system on the heart. This causes an increase in the heart rate and improves atrioventricular conduction.
500 µg IV or intra-orally (IO) can be given and repeated every 3–5 min to a total of 3 mg. It forms part of the resuscitation council algorithm for acute bradycardia.
62%
2nd line after atropine
Isoprenaline 5 micrograms per minute IV
Atropine can be given to a maximum cumulative dose of 3mg. Once this dose is reached there are several options including transcutaneous pacing, isoprenaline 5micrograms per minute, adrenaline 2-10 micrograms per minute
A 30-year-old gentleman with no past medical history has an ECG performed privately at the local GP. ECG reveals a sinus bradycardia of 37 beats per minute. The ECG is otherwise normal.
The patient confirms he is asymptomatic and that he is an avid athlete and exercises regularly. He is haemodynamically stable and has no chest pain.
How should this patient be managed?
Reassure and do nothing
This patient can be observed and discharged as he has no adverse features and is not at risk of asystole. His bradycardia results likely from vagal hypertonia due to being an avid athlete.
If called to see a patient on the ward with bradycardia, it would be prudent to assess the patient fully, excluding all other more sinister causes of bradycardia whilst following the algorithm carefully. It is important not to give a bolus of atropine intravenously unnecessarily
A 55 year old female presents to the emergency department complaining that her heart is missing a beat. She has a long standing history of lethargy, depression and constipation but takes no regular medication.
Her heart rate is 45 beats per minute but other observations are within normal range. Physical examination reveals no abnormalities. Her ECG shows a regular bradycardia, QRS complex duration of 84 ms and PR interval 100 ms.
What is the next best step in management?
Check thyroid function, electrolytes and observe
This is the correct answer. According to the ALS adult bradycardia algorithm, after assessing the patient with DRABCDE and ECG monitoring reversible causes must be identified such as electrolyte abnormalities. The history of depression, constipation and lethargy raises the suspicion of hypothyroidism which is a known cause of bradycardia, therefore checking thyroid levels is correct. This patient has no adverse features of bradycardia (shock, syncope, myocardial ischaemia or heart failure) and no risk factors for asystole, therefore observation alone is sufficient
The history of depression, constipation and lethargy raises the suspicion of
hypothyroidism which is a known cause of bradycardia, therefore checking thyroid levels is correct.
then atropine 500 mcg IV is given.
what is cardiac tamponade
Cardiac tamponade occurs when the accumulation of fluid, blood, purulent exudate or air in the pericardial space raises the intra pericardial pressure.
Subsequently, diastolic filling is reducing thereby reducing the cardiac output. It is a life threatening emergency that requires prompt diagnosis with echocardiogram and treatment.
signs and sx of cardiac tamponade
Symptoms
Typically, patients present with:
Shortness of breath
Tachycardia
Confusion
Chest pain
Abdominal pain
Signs
Signs of cardiac tamponade can be remembered by Beck’s Triad:
Hypotension
Quiet heart sounds
Raised JVP
trauma trauma trauma
This is the correct answer. The patient has clinical features of cardiac tamponade likely secondary to pericarditis. Quiet heart sounds, hypotension and raised JVP constitute Beck’s triad, however not all patients will present with all 3 features. His ECG shows small QRS complexes with electrical alternans which occurs with forward and backward movement of the heart within the fluid filled pericardium
cx of pericardiocentesis
Complications of this treatment include pneumothorax (all patients should have a CXR post procedure to exclude this) damage to the myocardium, coronary vessels, thrombus, arrhythmias/cardiac arrest and damage to the peritoneum
IX and MX of cardaic tamponade
Investigations
ECG - may show low voltage QRS complexes or electrical alternans
Chest X-ray - may show a large globular heart
ECHO - will demonstrate the amount of fluid around the heart and quantify the level of ventricular compromise.
Pericardiocentesis - will allow for sampling of the fluid to find the underlying cause and treat the immediate problem.
Management
First line management in patients that are haemodynamically unstable is pericardiocentesis.
In patients with haemopericardium, associated malignancy, traumatic/purulent effusion first line management is surgical drainage.
what causes right axis deviation - more positive
between +90 degrees to +180 degrees. Other causes of a right axis deviation include anterolateral myocardial infarct, right ventricular hypertrophy, left posterior hemi-block, Wolff-Parkinson White Syndrome with an accessory pathway on the left.]
Left–right-arm lead reversal
Incorrect lead placement such as left–right arm reversal leads to a negative complex in lead I with a negative P wave in lead I, as is seen in this patient. It is one of the commonest causes of right-axis deviation on an ECG. Although this was recognised by the physician, it should be repeated to confirm that this was the cause.
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