HISTORY, CURRENT ILLNESS AND PHYSICAL EXAMINATION
62-year-old man from León, who is in our health area on holiday. Currently retired, he worked as a boilermaker.

BACKGROUND:
Cardiovascular risk factors (CVRF): arterial hypertension, diabetes mellitus on treatment with oral antidiabetics with good control. Ex-smoker for 3 years of half a packet/day since youth (40 packets/year). No other toxic habits.
Previous cardiological history: refers to coronary angiography following exertional angina in another hospital with implantation of at least one stent (coronary anatomy unknown at the time of the initial anamnesis).
Chronic treatment: ranolazine, acovil, metoprolol, pantoprazole, metformin/vildagliptin, repaglinide, acetylsalicylic acid, pravastatin/fenofibrate.

CURRENT ILLNESS:
A 62-year-old male patient with the above-described history was referred to the emergency department for evaluation due to elevated markers of myocardial damage. The patient consulted for clinical symptoms of dizziness, general malaise and instability in the previous 24 hours. In addition, he reported atypical chest pain throughout the day, coinciding with the rest of the clinical picture, which he differentiated from his previous angina. He was accompanied by his wife, who was suffering symptoms of headache and dizziness similar to those of our patient.

PHYSICAL EXAMINATION:
Conscious, oriented, cooperative. Blood pressure (BP) 110/55 mmHg. Heart rate 77 bpm. Well perfused. Eupneic at rest without oxygen. Rhythmic heart sounds, no murmurs.
Bladder murmur preserved. Normal abdominal examination. Lower limbs without oedema.
Positive pedia bilaterally. No neurological focality.

COMPLEMENTARY TESTS
Haemogram: red blood cells 4.76 x10E6/μl, haemoglobin 13.6 g/dl, haematocrit 38.8%. MCV 81.5 fl.
MCH 28.6 pg. MCHC 35.1 g/dl. Leukocytes 14.73 x10E3/μl. Neutrophils (blood-%) 74.9%.
Neutrophils 11.03 x10E3/μl. Lymphocytes (%) 15.8%. Lymphocytes 2.33 x10E3/μl. Monocytes (blood-%) 9%. Monocytes 1.33 x10E3/μl. Eosinophils (blood-%) 0.1%. Eosinophils 0.01 x10E3/μl low (a).
Basophils (blood-%) 0.2%. Basophils 0.03 x10E3/μl. UPLAQ platelets 214 x10E3/μl. VPM 12.6 fl.
SR RDW Coefficient of variation 14.5%.
BIOCHEMISTRY: Glucose 449 mg/dl. Urea 94 mg/dl. Creatinine 1.4 mg/dl. Sodium ion 135 mmol/l. Plasma potassium ion 4.6 mmol/l.
ARTERIAL GASOMETRY: pH (arterial gas) 7.41, pCO2 (arterial gas) 31 mmHg low, pO2 (arterial gas) 71 mmHg low. Bicarbonate (arterial gas) 21.4 mmol/l. Total CO2 (arterial gas) 21 mmol/l. Excess bases (arterial gas) -4.5 mmol/l low. Oxyhaemoglobin saturation (arterial gas) 93% low. Carboxyhaemoglobin on admission 14%. Carboxyhaemoglobin after hyperbaric chamber normal.
MARKERS OF MYOCARDIAL DAMAGE: CK (U/L) 1985->2508 (at 24 hours)->441 (at 48 hours). TnT (ng/l, normal to 35) 1836->3828 (at 24 hours)->6000 (at 48 hours).
ELECTROCARDIOGRAM (ECG): sinus rhythm at 75 bpm. Signs of left atrial enlargement and left bundle branch block (LBBB).
THORAX RADIOGRAPHY: normal cardiothoracic index. No condensation or signs of heart failure.
Transthoracic echocardiography (TTE) (urgent): left ventricle slightly dilated with severe systolic dysfunction at the expense of akinesia of the middle and apical segment of the septum and global hypokinesia of the rest of the segments, more marked in the inferolateral and inferior wall. Right ventricle of normal size and systolic function. Left atrium of normal size. Aortic valve with good opening, slightly calcified.
Trivial mitral insufficiency. No indirect signs of pulmonary hypertension. Inferior vena cava not dilated. No pericardial effusion.
CORONARYGRAPHY: coronary arteries with irregularities, without significant lesions. Good appearance of the stent implanted in the right coronary artery (CD), which shows no significant restenosis.

CLINICAL EVOLUTION
Carbon monoxide poisoning was suspected (wood cooker at home) and carboxyhaemoglobin was requested, which turned out to be 14%, confirming the diagnosis. Hyperbaric chamber treatment was indicated with a session at 2.3 ATA, which left the patient asymptomatic and normalised carboxyhaemoglobin levels after 24 hours.

Given the marked elevation of biomarkers, cardiological assessment was requested after the hyperbaric chamber session. At that time the patient was asymptomatic in the anamnesis by systems, although the ECG showed complete left bundle branch block (LBBB), which we did not know if it was already known. An urgent echocardiogram was performed and showed a dilated left ventricle with impaired contractility and severe systolic dysfunction.
The patient was diagnosed with high-risk non-ST-segment elevation acute coronary syndrome (NSTEACS) secondary to carbon monoxide poisoning and was admitted to the coronary unit, under routine treatment and management. Twenty-four hours after admission, coronary angiography was performed, showing coronary arteries without significant lesions with good results of the stent previously implanted in the right coronary artery.
Subsequently, we were able to contact the patient's cardiologist, who informed us of the existence of LBBB and contractility alterations.

DIAGNOSIS
Carbon monoxide poisoning treated by hyperbaric chamber.
High-risk NSTEACS in the context of the above.
Dilated left ventricle with severely depressed LVEF. LBBB.
Ischaemic heart disease with 1-vessel disease (DC) with drug-eluting stent implantation in DC, with no evidence of thrombosis or restenosis.
