Comparison of changes in arterial blood pressure and cardiac output during cardiogenic shock development in a porcine model.

BACKGROUND

Low systolic blood pressure (SBP) is a key criterion for diagnosing cardiogenic shock (CS) caused by a reduction in stroke volume and cardiac output (CO). The temporal interaction between changes in pressure and flow has not been well described in the development of CS. In a large animal model, we assessed the temporal relationships of SBP, CO, and blood flow in the carotid artery during induction of CS.

METHODS

Fifteen adult Danish landrace pigs (median weight 71 kg) underwent CS induction by stepwise injection of polyvinyl alcohol microspheres into the left main coronary artery every 3 min to induce microvascular obstruction. After each injection, CO, SBP, and mixed venous saturation (SvO2) were recorded simultaneously from a ventricle sheath in the carotid artery and a pulmonary artery catheter in the right internal jugular vein. A Doppler flow probe measured blood flow in the left carotid artery. CS was defined as a ≥ 50% reduction in CO or SvO2 from baseline, or absolute SvO2 < 30%.

RESULTS

CS occurred after a mean of 8 (range 5 to 19) boluses of microspheres. SBP declined from 99 (± 15) mmHg to 74 (± 6) mmHg, equal to 74 (± 13)% of the baseline value. CO was reduced to 5.8 (± 0.7) L/min to 2.2 (± 1.3) L/min, equal to 38 (± 23)% and SvO2 from 63 (± 7)% to 37 (± 7)%, equal to 60 (± 13)% of baseline values. The decrease in CO was due to a reduction to 43 (± 26)% in stroke volume, as heart rate remained unchanged. The carotid artery blood flow was reduced from 285 (± 50) mL/min to 155 (± 56) mL/min, equal to 54% of baseline values. The decline in SvO2 and CO preceded a reduction in SBP, and after 25% of emboli were given, CO decreased by 24% while SBP was unchanged.

CONCLUSION

In a porcine model of ischemic myocardial injury, the decrease in blood flow and stroke volume preceded a decline in SBP, suggesting pressure preservation occurs in the presence of hypoperfusion.