Class of hemorrhagic shock is associated with progressive diastolic coronary flow reversal and diminished left ventricular function

Abstract

Introduction: The relationship between coronary artery flow and left ventricular (LV) function during hemorrhagic shock remains unknown. The aim of this study was to quantify coronary artery flow directionality alongside left ventricular function through the four classes of hemorrhage shock. Methods: Following baseline data collection, swine were exsanguinated into cardiac arrest via the femoral artery using a logarithmic bleed, taking each animal through the four classes of hemorrhagic shock based on percent bleed (class I: 15%; class II: 15%-30%; class III: 30%-40%; class IV: >40%). Telemetry data, left ventricular pressure-volume loops, and left anterior descending artery flow tracings over numerous cardiac cycles were collected and analyzed for each animal throughout. Results: Five male swine (mean 72 ± 12 kg) were successfully exsanguinated into cardiac arrest. Mean left ventricular end-diastolic volume, end-diastolic pressure, and stroke work decreased as the hemorrhagic shock class progressed (p < 0.001). The proportion of diastole spent with retrograde coronary flow was also associated with class of hemorrhagic shock (mean 5.6% of diastole in baseline, to 63.9% of diastole in class IV; p < 0.0001), worsening at each class from baseline through class IV. Preload recruitable stroke work (PRSW) decreased significantly in classes II through IV (p < 0.001). Systemic Vascular Resistance (SVR) is associated with class of hemorrhage shock (p < 0.001). Conclusion: With progressive classes of hemorrhagic shock left ventricular function progressively decreased, and the coronary arteries spent a greater proportion of diastole in retrograde flow, with progressively more negative total coronary flow. Preload recruitable stroke work, a load-independent measure of inotropy, also worsened in severe hemorrhagic shock, indicating the mechanism extends beyond the drop in preload and afterload alone.

Keywords: coronary artery flow; exsanguination cardiac arrest; hemorrhagic shock; left ventricular function (LV function); pressure-volume (P-V) loop.

FIGURE 1

Cartoon representation of the central instrumentation, with a PV loop in the left ventricle and the dissected left coronary artery with LAD coronary flow probe placement. Not shown is a peripherally inserted, solid-state pressure catheter for central venous pressure monitoring and a peripherally inserted solid-state pressure catheter for arterial blood pressure monitoring.

FIGURE 2

Mean arterial pressure (MAP), heart rate (HR), right atrial pressure (RAP), and whole blood lactic acid at each class of hemorrhagic shock (I-IV) induced by this logarithmic hemorrhage.

FIGURE 3

Analysis of oxygen delivery to the heart: (A) Hemoglobin and estimated percent of blood hemorrhaged from the logarithmic bleed at each study period, (B) myocardial oxygen delivery (DO2) from baseline and each class of shock, and (C) cardiac output from baseline and each class of shock.

FIGURE 4

PV loop analysis across baseline and each class of hemorrhagic shock (A) end-diastolic volume (EDV) and estimated percent blood hemorrhaged from the logarithmic bleed at each study period, (B) systemic vascular resistance (SVR) from baseline and each class of shock, and (C) preload recruitable stroke work (PRSW) from baseline and each class of hemorrhagic shock.

FIGURE 5

Representative ECG tracings (black) and coronary flow tracings (blue) superimposed on aortic pressures (red) over time (0.5 s) from one animal during baseline and each class of hemorrhagic shock (I-IV).

FIGURE 6

Analysis of coronary flow: (A) Coronary vascular resistance during diastole, (B) the percent of retrograde coronary flow during diastole at each class of hemorrhagic shock (I-IV), and (C) the coronary flow (mL/min; mean and standard deviation) at each class of hemorrhagic shock (I-IV).