Undifferentiated Palpitations — Written Clinical Reasoning

SAQ 1 — The Diagnostic Approach to Undifferentiated Palpitations (20 marks, 30 minutes)

Prompt: Outline your structured approach to the patient presenting with undifferentiated palpitations, addressing: (a) the four-descriptor classification; (b) the focused history questions that discriminate between the causes; (c) the focused examination; (d) the investigations — the mandatory 12-lead ECG, the bloods, the tiered ambulatory monitoring, the echocardiogram, the EP study; (e) the high-risk features; and (f) the cause-directed management. ^[1]

Model Answer

(a) The four-descriptor classification (3 marks): ^[1]

The classification of the palpitations by the symptom character narrows the differential before any test is ordered. The four descriptors are: ^[1]

1. Regular fast rhythm — the differential is sinus tachycardia (the physiological response to a systemic stimulus — fever, anxiety, anaemia, thyrotoxicosis, pregnancy, hypovolaemia, sympathomimetic drugs), paroxysmal supraventricular tachycardia (AVNRT, AVRT — the re-entrant circuits involving the AV node or an accessory pathway), and ventricular tachycardia (the re-entrant circuit in the scarred myocardium or the idiopathic outflow-tract VT).
2. Irregular rhythm — the differential is atrial fibrillation (the irregularly irregular pattern with no discernible P waves), atrial flutter with variable block (the regularly irregular pattern with the grouped beating), and frequent ectopic beats (the recognisable cadence of the normal-early-pause sequence).
3. Missed beat or extra beat sensation — the cardinal feature of the ectopic beats (atrial or ventricular); the patient perceives the compensatory pause after the ectopic as the missed beat, and the next sinus beat (with the larger stroke volume after the pause) as a thud.
4. Pounding or forceful sensation in a regular rhythm — the awareness of the increased stroke volume in the sinus rhythm; the differential is anaemia, thyrotoxicosis, pregnancy, fever, aortic regurgitation, the mitral valve prolapse, anxiety, and the sympathomimetic drugs (caffeine, salbutamol, pseudoephedrine). ^[1]

(b) The focused history questions (4 marks): ^[1]

The history is the most powerful investigation in the palpitations encounter. The six structured questions are: ^[1]

1. The onset: sudden or gradual? The sudden onset (the patient can name the moment) points to the re-entrant tachycardia (the SVT) or the initiation of the AF. The gradual onset (the rate climbs over minutes) points to the sinus tachycardia.
2. The duration: seconds, minutes, or hours? The seconds point to the ectopics or the non-sustained tachycardia. The minutes point to the SVT or the paroxysmal AF. The hours point to the persistent AF or the sustained VT.
3. The termination: sudden or gradual? The sudden termination (the rhythm switches off) points to the re-entrant tachycardia, often terminated by the vagal manoeuvre. The gradual termination (the rate drifts down) points to the sinus tachycardia. The terminating episode followed by the brisk polyuria is the SVT discriminator — the atrial natriuretic peptide drives the diuresis ^[2][6].
4. The triggers and the modifiers. The exercise-provoked palpitations are a red flag — the VT, the channelopathies (the LQT1, the CPVT), the structural disease (the HCM, the aortic stenosis). The substance-provoked palpitations (the caffeine, the alcohol, the cocaine) point to the triggered arrhythmia.
5. The associated symptoms. The syncope is the red flag (the haemodynamically compromising tachycardia). The chest pain may indicate the ischaemia or the atypical MVP pain. The dyspnoea indicates the loss of the atrial contribution to the filling. The polyuria is the SVT discriminator.
6. The drug, the family, and the past cardiac history. The drug history (the sympathomimetics, the QT-prolonging drugs, the antiarrhythmics). The family history of the sudden cardiac death under 40 (the channelopathies, the cardiomyopathies). The past cardiac history (the prior infarction, the cardiomyopathy, the valve disease, the congenital heart disease).

(c) The focused examination (3 marks): ^[1]

The examination has two goals: to identify a structural cardiac cause, and to identify a systemic cause. The examination is the full cardiovascular examination plus the thyroid. ^[1]

The vital signs — the pulse rate and rhythm (the apex-radial deficit of the AF), the blood pressure (the wide pulse pressure of the aortic regurgitation), the respiratory rate, the temperature, the oxygen saturation. The cardiovascular examination — the pulse character (the collapsing water-hammer of the aortic regurgitation), the apex beat (the location and the character — the thrusting volume-loaded apex, the pressure-loaded sustained apex, the double impulse of the HCM), the right ventricular heave, the heart sounds and the murmurs (the pansystolic of the MR, the early diastolic of the AR, the mid-systolic click and the late systolic murmur of the MVP, the mid-diastolic rumble of the MS). The thyroid examination — the goitre, the bruit, the eye signs of the Graves orbitopathy (the exophthalmos, the lid retraction, the lid lag, the ophthalmoplegia). The general examination — the pallor of the anaemia, the tremor of the thyrotoxicosis, the signs of the chronic disease. ^[1]

(d) The investigations (4 marks): ^[1]

The 12-lead ECG is mandatory for every patient with palpitations, no exceptions. The ECG may be normal between episodes in up to half of the patients with a documented arrhythmia, but it may reveal the substrate: the delta wave and the short PR of the WPW, the long QT (over 470 ms in a male, 480 ms in a female), the Brugada pattern (the coved ST elevation in V1 to V3), the left ventricular hypertrophy, the pathological Q waves of the old infarction, the right precordial T-wave inversions and the epsilon wave of the ARVC, the U waves of the hypokalaemia. ^[1]

The bloods — the full blood count (anaemia), the TSH with the free T4 (thyrotoxicosis), the urea and electrolytes with the magnesium (the electrolyte disturbances), the glucose, the drug levels if indicated. ^[1]

The ambulatory ECG monitoring is matched to the frequency of the symptoms. The 24 to 48-hour Holter for the daily symptoms. The patient-activated event monitor or the 14-day patch recorder for the weekly symptoms. The implantable loop recorder for the monthly or the rarer symptoms, or the unexplained syncope. A Holter for the infrequent palpitations is wasted effort ^[9].

The transthoracic echocardiogram is indicated for the suspected structural heart disease (the abnormal findings, the abnormal ECG, the high-risk history). It is not indicated for the patient with the normal history, the normal examination, and the normal ECG. ^[1]

The electrophysiology study is indicated for the confirmation and the ablation of the SVT, the induction and the mapping of the VT, and the risk stratification of the WPW (the antegrade ERP of the accessory pathway). ^[1]

(e) The high-risk features (3 marks): ^[1]

The five high-risk features that mandate the urgent cardiology referral are: ^[1]

1. The syncope or the near-syncope during the palpitations — the cerebral hypoperfusion from the haemodynamically compromising tachycardia.
2. The exertional symptoms — the VT, the channelopathies (the LQT1, the CPVT), the structural disease (the HCM).
3. The family history of the sudden cardiac death under the age of 40 — the channelopathies, the cardiomyopathies.
4. The structural heart disease — the prior infarction, the cardiomyopathy, the heart failure.
5. The abnormal ECG — the long QT, the Brugada, the epsilon wave, the right precordial T-wave inversions, the pathological Q waves, the LVH with the strain. ^[1]

(f) The cause-directed management (3 marks): ^[1]

The management is directed by the cause. The sinus tachycardia — treat the underlying cause. The SVT — the acute termination with the modified Valsalva manoeuvre, the adenosine (6 mg then 12 mg then 12 mg), the verapamil; the long-term management with the catheter ablation (the preferred definitive treatment, over 95 per cent success for the AVNRT and the AVRT) or the AV nodal blockers. The AF — the rate or the rhythm control, the anticoagulation guided by the CHA2DS2-VASc and the HAS-BLED, the direct oral anticoagulants preferred over the warfarin for the non-valvular AF. The ectopic beats — the reassurance and the trigger avoidance in the normal heart, the beta-blocker for the highly symptomatic, the cardiology referral for the ectopy burden over 10 to 15 per cent or the structural heart disease. The VT — the urgent cardiology referral, the synchronised DC cardioversion if unstable, the intravenous amiodarone if stable, the ICD for the secondary prevention. The channelopathies — the specialist evaluation, the beta-blockade, the left cardiac sympathetic denervation, the ICD for the high-risk. ^[1]