Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy (1 per 200 with an inherited cardiomyopathy) . Half of all patients with HCM present with symptoms such as dyspnea on exertion, chest pain or dizziness, irrespective of the degree of left ventricular hypertrophy or obstruction . These functional limitations can seriously affect the patient’s quality of life, both professional and private. The primary medical treatments proposed are beta-blockers or calcium antagonists, which have varying levels of efficacy and substantial potential side-effects . We report the first series, of six patients, exhibiting impressive improvement following administration of midodrine hydrochloride.

The first patient, aged 45 years with a history of obstructive HCM, was admitted in April 2015 for orthostatic hypotension, confirmed by a positive tilt-table test. He also complained of significant discomfort when walking (New York Heart Association [NYHA] class II). Treatment did not prevent several lipothymic and syncopal episodes ( Table 1 ). Although the echocardiography work-up revealed no left ventricular outflow tract obstruction (LVOTO) at rest, the maximal gradient during exercise was recorded at 50 mmHg, reaching 100 mmHg in the early recovery phase. Considering the patient’s orthostatic hypotension, midodrine hydrochloride treatment was proposed. This drug produces a direct and selective sympathomimetic effect on peripheral alpha-adrenergic receptors, resulting in vasoconstriction of first the veins and then the arteries. After 1 month of treatment, consultation records reported no recurrence of faintness, less shortness of breath during exercise (NYHA class I), and no LVOTO.

Table 1

Characteristics, treatment and results in six patients with HCM treated with midodrine hydrochloride.

Patient number	1	2	3	4	5	6
Characteristics
Sex	Male	Female	Male	Male	Male	Female
Age (years)	45	67	66	53	65	64
HCM type	Maron subtype 3 (MYH7 mutation) Maximal wall thickness: 14 mm	Maron subtype 2 (MYH7 mutation) Maximal wall thickness: 16 mm	Maron subtype 2 Maximal wall thickness: 17 mm	Maron subtype 2 Maximal wall thickness: 22 mm	Maron subtype 3 Maximal wall thickness: 17 mm	Maron subtype 1 Maximal wall thickness: 15 mm
Regular treatment (per day)	80 mg nadolol	None (beta-blockers, verapamil not tolerated)	2.5 mg carvedilol 200 mg amiodarone 20 mg rivaroxaban	120 mg nadolol	120 mg verapamil	5 mg carvedilol
Midodrine
Reason for initiation	Orthostatic hypotension	Orthostatic hypotension	Positive leg-raise test	Positive leg-raise test	Positive leg-raise test	Orthostatic hypotension
Dosage (mg/day)	2.5 mg × 2	2.5 mg × 3	5 mg × 4	5 mg × 3	5 mg × 3	5 mg × 3
Side-effects after midodrine introduction	None	Piloerection, warming extremities	None	Some hot flushes	None	None
Discontinuation	No	No	No	No	No	No
Total duration (days)	55	30	24	7	7	7
Symptoms
Before midodrine introduction	Dizziness and syncope on exertion NYHA class II dyspnea	Chest pain NYHA class III dyspnea	Pulmonary oedema NYHA class IV dyspnea	NYHA class II dyspnea	Chest pain NYHA class II dyspnea	Chest pain NYHA class II/III dyspnea
After midodrine introduction	None NYHA class I	None	None	None	Reduced chest pain occurrence NYHA class I/II dyspnea	NYHA class I/II
Delay to onset of symptom release (days)	3	2	1	2	1	2
Leg-raise test a	NA	Positive	Positive	Positive	Positive	Positive
Echocardiography findings
LVOT obstruction	Yes	Yes	Yes	Yes	Yes	Yes
Maximal LVOT gradient (mmHg) at rest
Before	7	88	100	70	60	40
After	10	50	10	30	60	50
Maximal LVOT gradient (mmHg) at peak exercise
Before	50	145	NA	80	90	100
After	13	95	45	50	70	80
Maximal LVOT gradient (mmHg) at recovery
Before	100	90	NA	80	120	110
After	15	95	45	50	90	90
Other investigations	Positive tilt-table test	Normal coronary angiogram	Normal coronary angiogram	Normal coronary angiogram	Normal coronary angiogram	No significant stenosis
Last follow-up (days)	45	30	24	7	7	19
Outcome	No symptoms NYHA class I	No symptoms NYHA class I	No symptoms NYHA class I	No symptoms NYHA class I	Reduced chest pain occurrence NYHA class I/II dyspnea	No symptoms NYHA class I

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