Doppler Evaluation of Changing Cardiac Dynamics during Cheyne-Stokes Respiration: Methods
Patients were examined in the supine or left lateral decubitus position using standard two-dimensional and pulsed Doppler echo-cardiographic techniques. Studies were recorded using commercially available echocardiographs and analyzed with a commercially available graphics analysis system. All studies were performed by one experienced echocardiographer.
Left ventricular inflow velocity profiles were obtained from an apical four-chamber view with the pulsed-Doppler sample volume positioned at the tips of the mitral valve leaflets.
Left ventricular outflow velocity profiles were obtained from either the apical long-axis or suprasternal view with the pulsed Doppler sample volume positioned in the left ventricular outflow tract just beneath the aortic valve (two patients) or within the proximal ascending aorta (eight patients). Doppler sample placement was selected for the most reproducible velocity profile that could be obtained during hyperpnea and apnea and was kept constant for the remainder of the study. More info
Although the changes in the flow velocity profiles could be monitored throughout both phases of Cheyne-Stokes respiration in some patients, most patients exhibited sufficient mediastinal movement during hyperpnea to preclude continuous, accurate recordings, and thus, the periods of end-hyperpnea and end-apnea were chosen for statistical analysis. All values represent the average of two to five consecutive cardiac cycles for each phase of respiration. The differences between the two phases of respiration were analyzed utilizing the paired Students t-test.
Cyclic changes in the transmitral flow velocity profile were noted. Measured peak E and peak A velocities and E and A integrals at two convenient points of the breathing cycle (end-hyperpnea and end-apnea) are shown in Table 1.
Table 1—Left Ventricular Inflow Flow Parameters (n = 10)
|End Hyp||End Ap||p value|
|Mean LVI, cm/s||34.1 ±10.8||27.6 ±10.0||<0.01|
|Peak E, cm/s||82.9 + 20.7||59.9 ±18.1||<0.001|
|Peak A, cm/s||31.7+16.8||39.3 ±22.8||<0.05|
|Peak E/A ratio||3.0 +1.3||1.7 + 0.6||<0.01|
|VTI||13.0 ±4.9||10.0 ±5.0||<0.001|
|E int||9.8 ±3.8||6.1 ±2.9||<0.001|
|A int||2.8± 1.7||3.3±1.9||NS|
|Int E/A ratio||3.9± 1.8||2.0±0.8||<0.05|
|HR per min||77.3 ±10.0||76.2 ±10.0||NS|
|Diastolic filling time, s||0.38 ±0.10||0.37 ±0.09||NS|