Recent modifications in intra-aortic balloon pumping (IABP) catheters have increased the ease of use, extended clinical indications, and reduced the incidence of vascular complications. These major technical advances include the introduction of low-profile catheters1 and facilitation of percutaneous insertion through sheath introducers.2 Intra-aortic balloon pump is thus currently applied in various clinical conditions, including high-risk percutaneous coronary intervention (PCI), unstable angina, and refractory ventricular arrhythmia, with fewer incidences of vascular complications than reported before.3 In fact, several early clinical studies conducted with IABP catheters ranging in size from 8 to 12 French (12 Fr) have confirmed the impact of low-profile IABP catheters on the incidence of vascular complications, especially limb ischemia.4–7 These findings have encouraged the development of even smaller IABP catheters, and 7 or 7.5 Fr IABP catheters are currently used extensively in daily clinical practice. Furthermore, a 6 Fr IABP catheter has been developed and distributed for clinical use in Japan8 for reduction in the rate of vascular complications. However, the feasibility and safety of using this 6 Fr IABP catheter have not yet been clarified. In this study, we retrospectively analyzed the clinical outcome of 69 patients who underwent PCI with the 6 Fr IABP catheter with a balloon volume of 30 ml.
Between January 2007 and December 2011, 234 patients at our institution underwent PCI with IABP catheters. Of these, 69 patients received 6 Fr IABP catheters. Patients with height <162 cm were primarily selected for the 6 Fr IABP catheter treatment because of the limited balloon volume of this catheter (30 ml). These catheters were also used for patients for whom the femoral approach was contraindicated, regardless of body size. The clinical outcomes of all patients were evaluated at the time of discharge. This study was approved by the institutional review board.
Intra-Aortic Balloon Pumping Catheters and Insertion Procedure
The 6 Fr IABP catheter (Zeon Medical Corp., Tokyo, Japan) used in this study had a balloon volume of 30 ml. After a 6 Fr introducer was inserted, a dedicated 0.014 inch guidewire and balloon catheter were introduced. The guidewire was retrieved, and a dedicated stylet was inserted to reinforce the catheter shaft before balloon pumping was initiated. The length of the catheter shaft is 52.4 cm, which is the longest among 7.5 Fr or smaller catheters currently available. Because of this feature, this balloon catheter is suitable for the brachial approach. The insertion procedure and device use were according to the manufacturer’s instructions. For balloon pumping, a Zemex IABP console 97 (Zeon Medical Corp.), a Datascope CS 100 (Datascope Corp. Mahwah, NJ), or system 97 (Datascope Corp.) was used.
Hemostasis After Retrieval of the IABP Catheter
In the case of patients for whom the procedure was conducted via the femoral approach, manual compression was applied for approximately 15 min (or more, if required) to complete hemostasis and via the brachial approach, Tometa-kun (Zeon Medical Corp.), a hemostatic device that enables pneumatic compression,9 was used.
The parameters used for patient evaluation were as follows: 1) in-hospital mortality, including that when the balloon was in place and that directly related to IABP insertion; 2) access site complications, including major bleeding defined as large hematoma formation or bleeding at the balloon insertion site, retroperitoneal hemorrhage, leading to hemodynamic compromise and requiring longer bed rest, transfusion, or surgical intervention; limb ischemia defined as loss of pulse or sensation in the limb, and abnormal limb temperature or pallor requiring surgical intervention or amputation related to the IABP access site; 3) IABP failure, including balloon leak and poor inflation; and 4) insertion difficulty, including failure to place the balloon at the right position because of poor catheter pushability or loss of the support of the dedicated guidewire against the tortuosity of the vessel. All these parameters were evaluated by the insertion of the IABP catheter to discharge.
Baseline Characteristics of the Patients
For the 69 patients treated with the 6 Fr IABP catheters, the mean age and proportion of women were 76.9 years and 47.8%, and the average height and body weight were 156.7 cm and 56.0 kg, respectively. Percutaneous coronary intervention was performed via the transradial approach in 53 of these patients, the femoral approach in 13 patients, and the brachial approach in three patients. Fifty-six patients received IABP under emergency conditions: 44 had acute coronary syndrome, including five with cardiopulmonary arrest on arrival and four who required extracorporeal membrane oxygenation, and 12 patients presented with hemodynamic deterioration during elective PCI. The remaining 13 patients underwent prophylactic PCI. The mean observation period was 48.6 ± 83.7 days (0–398 days; Table 1).
Insertion and Management of the IABP Catheters
The 6 Fr IABP catheters were inserted through the femoral artery in 65 (94.2%) of the 69 patients. In the remaining four patients for whom the femoral approach was contraindicated, the 6 Fr IABP catheters were inserted via the brachial artery. Insertion and the subsequent balloon pumping were successful in all cases, and clinically sufficient diastolic augmentation was achieved, even in patients in whom the catheter was introduced through the brachial artery. The mean hemodynamic support time with IABP was 49.8 ± 71.2 h.
The in-hospital mortality was 7.2%, and no IABP catheter-related death occurred before discharge. No patients experienced limb ischemia, including the patient treated with brachial approach. Initially, all patients had sufficient augmentation; however, during the course of time, one patient showed poor helium inflation necessitating catheter exchange that occurred with femoral approach. In this patient, a kink was found in the shaft at the point of exit of the introducer, which may have been formed during insertion. Helium leakage was observed in one patient with femoral approach, in which case the IABP catheter was retrieved and replaced with a 7 Fr Datascope IABP catheter with a volume of 30 ml. None of the patients required the catheter to be switched to one with a larger balloon size because of insufficient augmentation with time (Table 2).
In this study, we demonstrated that hemodynamic support with a 6 Fr IABP catheter is feasible in select patients. We also showed that a 6 Fr IABP catheter can be safely inserted through the brachial arteries.
One of the advantages of small IABP catheters is that there are fewer vascular complications. In several studies performed during the late 1980s, the incidence of severe limb ischemia was reported to be 8.3–11.7%1,10–13; however, in the late 1990s, the incidence was reported to have reduced to 3.3–4.0%.14–16 More recently, a study that compared the outcome between patients who underwent IABP with 8 and 9.5 Fr catheters showed that the 8 Fr IABP catheter was superior to the 9.5 Fr catheter regarding the incidence of limb ischemia.4 In fact, no patients in this study (n = 69) experienced limb ischemia, whereas seven patients treated with 7 or 7.5 Fr IABP catheter during the same period developed limb ischemia (n = 165).
Another advantage of using small catheters is the resolution of access site limitations. Despite several concerns, including vascular complications and balloon pumping with the retrograde position of the balloon in the aorta, brachial insertion of 7 and 7.5 Fr IABP catheters is considered feasible and safe17,18; however, the 6 Fr IABP catheter used in the current study is considered safer because of its smaller shaft size. In addition, this catheter has the longest shaft among the small catheters (7.5 Fr or smaller). Therefore, it is suitable for use via the brachial approach, which requires a longer shaft than that required in the femoral approach.
On the contrary, reducing the size of IABP catheters raises several concerns. First, the narrow lumen for helium passage may compromise the response to a trigger. Technical data from the manufacturer of the IABP catheter indicated that the shuttle time to complete a single round of inflation and deflation with balloon volume of 30 ml when operated with Xemex IABP console 908 was 237 ms with a 6 Fr IABP catheter but 180 ms with a 7 Fr and 156 ms with an 8 Fr catheter. The typical dP/dt of the balloon examined in vitro was 1272.4 mmHg/s for the 6 Fr catheter; 1603.2 mmHg/s for the 7 Fr catheter; and 1957.1 mmHg/s for the 8 Fr IABP catheter. These data indicated that during the time required to reach the peak pressure of the balloon, the 6 Fr catheter takes 1.5 times longer than the 8 Fr catheter. These differences in the transportation of helium gas may influence the efficiency of balloon pumping under critical settings. Second, as observed in this study, the catheter shaft may kink during insertion, which could cause narrowing or closure of the inner lumen and eventually lead to insufficient dilatation. To avoid this, balloon pumping should be initiated after the completion of stylet insertion. Third, the thinness of the balloon may make it prone to helium leaks. In this study, balloon leakage occurred in one case (1.4%). Although this incidence is identical to that reported recently in the case of larger IABP catheters,19,20 it is nonetheless a problem. Fourth, only a 6 Fr balloon catheter with a volume of 30 ml is currently available; therefore, only a limited number of patients qualify for treatment with this catheter. In the present series, the mean body surface area of patients who underwent PCI with the 6 Fr catheter was 1.52 m2, which is rather low compared with that of the general Japanese population (1.73 m2).21 Finally, it is not possible to monitor aortic pressure through the wire lumen because of the presence of the stylet. Basically, limitations of this catheter may have to be considered when applying it to patients especially with femoral approach.
The change in diameter from 7 or 7.5 Fr to 6 Fr is <1.0 mm; yet, the results of the current study are promising for prevention of limb ischemia in the small-sized patients.
Although several concerns remain, the 6 Fr IABP catheter is feasible in clinical use for small-sized patients and may have the potential benefits of reducing their vascular complications. The brachial approach with the 6 Fr IABP catheter is also feasible. Thus, this catheter is considered useful for patients in whom femoral insertion is contraindicated. To confirm the findings in the current study, further large-scale randomized studies are warranted.
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