HISTORY, CURRENT ILLNESS AND PHYSICAL EXAMINATION
64-year-old woman with no personal history of interest. No previous cardiological history. She does not take any medication.
She came to the emergency department of our hospital with progressive dyspnoea for the last 1 week.
She also reported self-limited episodes of palpitations, lasting minutes, which have been occurring daily for the last 6 months. No other symptoms were reported.
Physical examination: blood pressure (BP) 120/70 mmHg, heart rate (HR) 125 bpm, oxygen saturation (SatO2) 95%. Conscious, oriented, eupneic at rest. No jugular venous engorgement. Cardiopulmonary auscultation: arrhythmic, tachycardic, no murmurs.
Bybasal crackles. No oedema in the lower limbs.

COMPLEMENTARY TESTS
ELECTROPHYSIOLOGICAL STUDY.
ECG.
THORAX RADIOGRAPHY: cardiothoracic index at the upper limit of normality, signs of vascular redistribution, free costophrenic sinuses.
ANALYSIS: normal haemogram. Biochemistry with normal creatinine and ions. N-terminal pro-brain natriuretic peptide (NT-proBNP) 2115.
E C O C A R D I O G R A M A : moderate left ventricular dysfunction (LVEF 35%), mild right ventricular dysfunction.
Mild left atrial dilatation. Mild mitral and tricuspid insufficiency. Normal pulmonary artery pressure. Compatible with tachycardiomyopathy. Study performed in sinus rhythm.

CLINICAL EVOLUTION
Given the presence of a narrow QRS tachycardia with a regularly irregular pattern, it was decided to perform vagal manoeuvres, observing the cessation of the tachycardia with early recurrence as seen in the ECG. Looking closely at the ECG, one can see what looks like a p-wave for every two QRS with a constant interval, also, in one of the ECGs one can see a beat with an image of complete right bundle branch right bundle branch block (RBBB). This could correspond to an anterograde dual nodal pathway tachycardia, as confirmed by the electrophysiological study performed during admission.
At the same time, as the patient was in heart failure, depletive treatment was started with a good response. The echocardiogram showed a non-dilated left ventricle with severe systolic dysfunction and global hypokinesia. Treatment was therefore started for heart failure with reduced ejection fraction, beginning with enalapril 2.5 mg (twice a day), bisoprolol 2.5 mg (1 tablet at breakfast) and eplerenone 25 mg (1 tablet at breakfast).
During admission, a coronary computed tomography (CT) scan was performed, which ruled out significant lesions in the coronary arteries.
It was decided to proceed with ablation of non-reentrant intranodal tachycardia, with success, and she was discharged a few days later.
After 4 months, a control echocardiogram was performed with normalisation of ventricular function, and the patient was asymptomatic.

DIAGNOSIS
Double nodal anterograde tachycardia.
Probable tachycardiomyopathy in relation to previous findings.
