Cardiogenic shock occurs in 5 to 8% of patients hospitalized with ST-elevation myocardial infarction [1]. Despite aggressive treatment modalities such as PCI and use of intra-aortic balloon support, mortality of cardiogenic shock remains at 50–70 % [5]. Recovery of myocardial performance following successful revascularization of the infarct-related artery may require several days [5]. During this period, many patients develop low cardiac output [5], and mechanical circulatory support is used to prevent hemodynamic instability. The IMPELLA® is a minimally invasive assisted circulation device that can be implanted using a catheter technique and has efficacy and safety in patients presenting with cardiogenic shock [6]. The IMPELLA® has been approved by the US Food and Drug Administration for use in patients with cardiogenic shock for up to 6 days and for high-risk coronary interventions for up to 6 h [7, 8].
Guidelines for optimal IMPELLA® placement stipulate that the inlet of the IMPELLA® should be 35 mm below the aortic valve and the outlet should be above the aortic valve [7, 8]. The IMPELLA® is equipped with a position-sensing aperture on top of the discharge, and the position waveform is displayed on a monitor. However, no position waveform abnormality was detected in this case, and Kaki et al. emphasized the importance of using imaging modalities such as TTE and TEE to check for abnormalities in IMPELLA® position [6]. Frequent complications with IMPELLA® utilization include acute limb ischemia, insertion site bleeding, hemolysis, and vascular complications [4]. Left ventricular perforation by an IMPELLA® has occurred in 25 of 407 patients (6.1%) based on the MAUDE database [9]. However, only three cases have been reported worldwide [2,3,4], and only one of them used TEE. In this case, TEE showed that IMPELLA® inlet was not visible and the entire IMPELLA® was implanted 4–4.5 cm deeper than the aortic valve level [2], which played an important role in detecting the abnormal position of IMPELLA®.
In the setting of transmural infarct, there is a particular need for caution regarding complications following IMPELLA® placement. The histopathologic sequence after ST-elevation myocardial infarction is well characterized and any ventricular instrumentation poses a higher risk than in a normal setting [4]. The possibility of IMPELLA®-induced left ventricular perforation should be considered if new pericardial effusion is detected, the positional waveform of the IMPELLA® monitor changes, or heart failure progresses rapidly [2]. In the present case, TTE showed increased pericardial fluid and findings suggestive of free wall rupture. It was difficult to identify the precise perforation site on TTE, but TEE showed that the tip of the IMPELLA® had strayed into the apical wall of the left ventricle. TEE was also useful in identifying the perforation site.
The IMPELLA® tip has an inlet slightly in front of the tip and a pigtail catheter protruding from the tip [10]. In the present case, an IMPELLA CP® was used, with a pigtail catheter of 6 Fr and a cannula of up to 14 Fr at maximum. Two highly echogenic parallel lines that appeared to be the IMPELLA® tip strayed into the apical wall of the left ventricle based on TEE findings. On TEE, it was not possible to distinguish the difference between the pigtail catheter and the cannula. The tip was not visible from the surface of the heart and was only palpable at a point on the free wall where bleeding and thinning were observed. This suggests that only the tip of the pigtail catheter may have perforated the left ventricular free wall.
The perforation site coincided with the dominant region of the left anterior descending branch #7, which was completely occluded, suggesting that left ventricular perforation was caused by weakening of the myocardium. If left ventricular perforation by an IMPELLA® is suspected, the IMPELLA® should not be repositioned or removed immediately to avoid catastrophic bleeding [4]. Under cardiopulmonary bypass, the site of perforation should be confirmed and the IMPELLA® should then be carefully removed. It is not clear when left ventricular perforation occurred in the present case. In a past report, the IMPELLA® migrated deep into the left ventricle and subsequently eroded through the wall during transportation of the patient [2]. However, the report did not include any information on the implantation procedure or postprocedural monitoring at the referring center. Ventricular perforation by a 6-Fr end-hole catheter, such as the multipurpose catheter used for indwelling, is common [11].
In our case, PCI under PCPS and IABP support was performed for cardiogenic shock, but due to prolonged hypotension, the IABP was removed and an IMPELLA® was placed instead. TEE showed that the tip of the IMPELLA® strayed into the apical wall of the left ventricle, and TEE was useful for identifying the site of perforation. The tip of the IMPELLA® must be implanted in the left ventricle, but the fragile left ventricular wall due to infarction can be easily perforated. It is extremely important for us anesthesiologists to keep track of the proper placement of the IMPELLA® at all times via various monitors, including TEE, in anticipation of situations such as this case.
