What does a "W" shape during IABP inflation signify?

The presence of a "W" shape during intra-aortic balloon pump (IABP) inflation indicates late inflation timing. This distinct pattern emerges when the balloon is inflated later than the optimal timing in relation to the cardiac cycle, specifically during diastole. When the balloon inflates at the correct time, it provides effective assistance to the heart by reducing left ventricular workload and increasing coronary perfusion. However, if the inflation occurs too late, it can coincide with the ejection phase of the cardiac cycle when the heart is actively contracting.

This can lead to suboptimal hemodynamic support and a decrease in efficacy, which manifests as the "W" shape on the waveforms or pressure tracings. Recognizing this pattern is critical for clinicians operating IABPs, as it signals the need to adjust the timing of inflation for improved outcomes.