History
A 24-year-old man was in a pub when he suddenly collapsed. When the paramedics arrived he had come around and an ECG was performed (Fig. 28.1). He described feeling palpitations prior to his collapse and has had this before. He was feeling unwell, cool and clammy. His blood pressure was 101/72 mmHg. He was taken to the emergency department.
Examination
This young man became more unwell and drowsy. His blood pressure on arrival was 60/40 mmHg. A new ECG was performed (Fig. 28.2).
Initial treatment
He underwent urgent synchronized DC cardioversion which restored him to sinus rhythm.
Cardiovascular and respiratory examination was normal. He was taken to the coronary care unit for monitoring.
Figure 28.1
Figure 28.2
Questions
• What is the underlying diagnosis?
• What caused this patient to decompensate?
• How should he be managed?
Figure 28.1 demonstrates a short PR interval with a slurred onset of the QRS waveform (delta wave). When associated with a supraventricular tachycardia the diagnosis is Wolff–
Parkinson–White (WPW) syndrome. The cause of the delta wave is due to an accessory conduction pathway that is separate from the usual AV node/bundle of His–Purkinje conduction pathway. The extra pathway connects the atria to the ventricles. During sinus rhythm the SA node activates both conduction pathways, resulting in depolariza-tion of the ventricles from two separate places. As a result the PR interval is shortened and there is a slurred upstroke (delta wave) at the beginning of ventricular depolariza-tion. The delta wave is seen in sinus rhythm and not during tachycardias associated with WPW. Sometimes the pathway is ‘concealed’; i.e. there is no short PR interval and slurred upstroke as there is no antegrade conduction. A tachycardia can result if a re-entry circuit is set up involving the accessory pathway and the normal AV nodal pathway. As there is no AV node in the accessory pathway to limit atrial conduction, ventricular rates can be very fast. This has the potential to cause syncope, haemodynamic compromise or sudden death. However, sudden death is rare (estimated frequency of 0.1 per cent).
In the presence of atrial fibrillation the re-entry tachycardia can be potentially fatal.
Very fast fibrillation causes rapidly conducted rates of above 220/min which can trigger ventricular fibrillation. This occurrence is quite rare. In this case his rhythm has changed to atrial fibrillation with rapid conduction to the ventricles causing him to decompensate.
The immediate management in anyone with unstable tachycardia is urgent synchronized DC cardioversion. If the patient is haemodynamically stable but the ECG demonstrates a regular tachycardia, then AV node blocking medications can be used. If this does not work, electrical cardioversion is used. If the underlying rhythm is AF, avoidance of AV blocking drugs like digoxin, adenosine, calcium-channel antagonists and beta-blockers is important. Intravenous amiodarone or procainamide can be used as these drugs prolong the refractory period of the accessory pathway. Again, electrical cardioversion is required if there is no response to medications. An echocardiogram should be performed to rule out structural heart abnormalities that are associated with accessory pathways (Ebstein’s anomaly and hypertrophic cardiomyopathy). Long-term management will require referral to an electrophysiologist to consider ablation of the pathway.
KEY POINTS
• An ECG with a short PR interval and delta wave describes the WPW pattern – its association with palpitations and SVT describes the syndrome. However, the WPW pattern is absent in concealed pathways.
• WPW syndrome is associated with sudden death but the incidence of this is extremely rare.
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CASE 29:
ECCHYMOSISHistory
A 31-year-old woman has presented to the emergency department with significant bruis-ing on her arms and legs that has been gettbruis-ing worse. She first noticed them five days ago when they started off as small bruises. She intended to visit her GP but noticed they were now larger and more widespread. She has had no fevers, arthralgia or recent viral infections, and she is not taking any medications.
Examination
This woman looks systemically well. There is a marked petechial rash over her legs with large bruising on the arms and legs. A cardiovascular and respiratory exam is normal. On abdominal examination there is no hepatosplenomegaly and there is no lymphadeno pathy. Observations: temperature 36.8°C, heart rate 78/min, blood pressure 135/67 mmHg, respiratory rate 18/min, SaO2 98 per cent on air.
INVESTIGATIONS
Normal range
White cells 6.0 4–11 ¥ 109/L
Haemoglobin 11.1 13–18 g/dL
Platelets 15 150–400 ¥ 109/L
Sodium 133 135–145 mmol/L
Potassium 3.7 3.5–5.0 mmol/L
Urea 5.4 3.0–7.0 mmol/L
Creatinine 65 60–110 mmol/L
INR 1.0 0.9–1.1
APTT 23 18–28 s
Blood film Reduced platelet count, no abnormal white cells
Questions
• What is the most likely diagnosis?
• How should this patient be managed?
The main abnormality in the results is the very low platelet count. The most likely diag-nosis is idiopathic thrombocytopenic purpura (ITP). However, she requires other investi-gations to exclude causes such as B12 or folate deficiency, acute leukaemia or sepsis. An abdominal ultrasound should be performed to check the size of the spleen and look for any other masses as an enlarged spleen indicates an alternative diagnosis. An HIV test is also advised. Bone marrow aspirate and biopsy can determine whether platelet produc-tion is normal and hence the likely cause of low platelets is immune-mediated antibody destruction in the spleen. In general a bone marrow biopsy is not required in a young, systemically well person but would be considered if there were other features suggesting an alternative diagnosis or failure to respond to treatment. In the absence of medications and infective causes, ITP is the likely cause.
Her bruising is worsening and, based on her history, examination, platelet count and blood film, ITP should be treated with intravenous immunoglobulin and prednisolone.
If there is life-threatening bleeding, such as an intracranial bleed, platelet transfusion in addition to immunoglobulin/steroid therapy can be given. Tranexamic acid can also be administered as this helps to inhibit fibrinolysis and stabilize clot formation.
If bleeding is uncontrolled despite therapy, a splenectomy can be performed.
KEY POINTS
• Idiopathic thrombocytopenic purpura is a diagnosis of exclusion and there is no confirmatory test for it.
• If the spleen is enlarged then another cause is more likely, such as systemic lupus erythematosus (SLE).
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