Dynamic Variation of Impedance Cardiography(DYVIC) as a Diagnostic Tool of Acute Heart Failure (AHF)

Acute heart failure (AHF) is a frequent condition in emergency department and is responsible of high number of admissions, complications, and deaths.

despite advances in diagnostic techniques, AHF diagnosis still be challenging .

Measurement of cardiac output (CO) is used to evaluate global cardiac function and changes in CO may be used to identify a change in the hemodynamic status of patient.

the gold standard of measuring CO is thermodilution catheterization, however it is an invasive technique with high risks.

Impedance cardiography (ICG) is a noninvasive method for measuring CO. it is performed by applying small electrical current to the chest through electrodes placed on the neck and sides.

the pulsatile flow of blood causes fluctuations in the current, and the device calculates CO from the impedance waveform.

In practice, the investigators connect the device "BIOPAC" by using four electrodes which the investigators place on the base of the neck (posterior face) and on the base of the thorax (posterior face).

The ECG recording is taken simultaneously with two other electrodes placed at the right upper limb and left lower limb.

In addition to detecting the electric current and the ECG, heart sounds are recorded using a sensor that is placed at the mitral site.

Each patient is initially placed in a semi-sitting position at 30° for 5 minutes and then CO is measured (baseline CO). NTG (0.6 mg) is then given to the patient sublingually and CO measurement was repeated. CO is calculated by averaging three measurements at one minute intervals at baseline and after NTG administration. DeltaCO was defined as the percent of change of baseline CO after NTG test.

Inclusion criteria

• 18 year old or above non traumatic acute dyspnea

Exclusion criteria

• ECG diagnostic for acute myocardial infarction or ischemic chest pain within the prior 24 hours,
• pericardial effusion ,
• chest wall deformity suspected of causing dyspnea,
• coma,
• need for mechanical ventilation or vasopressor drugs,
• serious and sustained arrhythmia,
• pace maker,
• severe mitral valve disease, severe pulmonary arterial hypertension,
• renal failure (creatinine >350µmol/l.