Summary
Aim
Cardiogenic shock is associated with high mortality. We report our experience with the short-term left ventricular axial pump Impella LP5.0 in nine patients with severe ischaemic heart failure.
Methods
Six patients (group 1) presented with cardiogenic shock at the acute phase of an ST elevation myocardial infarction. Three patients (group 2) had severe ischaemic cardiomyopathy with temporary contra-indication to LVAD or transplantation. We measured haemodynamic and metabolic variables up to 96 hours and recorded morbidity, mechanical pump failures, and mortality up to one year postimplantation.
Results
In all patients the Impella LP5.0 was safely placed through the right subclavian artery. Cardiac power output increased from 0.64 (0.07) W to 0.94 (0.44) W and 1.02 (0.30) W at 24 and 72 hours, respectively. The Impella LP5.0 remained in place for 12 (7.2) days. In group 1, five patients were in INTERMACS Profile 3 at the time of pump insertion. Three could be weaned and survived. One patient in INTERMACS Profile 1 died of intractable heart failure within hours. In group 2, two of three patients underwent heart transplantation. Haemorrhage requiring transfusions was observed in four patients but only one case was directly related to the Impella LP5.0.
Conclusion
Left ventricular assistance with the Impella LP5.0 appears to be well tolerated. It may be especially useful in patients with acute myocardial infarction complicated by cardiogenic shock who achieve INTERMACS Profile 3 with initial treatment.
Résumé
Objectif
Le choc cardiogénique est associé à une mortalité élevée. Cette étude rapporte notre expérience avec la pompe axiale Impella LP5.0 chez neuf patients atteints d’insuffisance cardiaque sévère d’origine ischémique.
Méthodes
Six patients (groupe 1) présentaient un choc cardiogénique à la phase aiguë d’un infarctus du myocarde avec sus-décalage du segment ST. Trois patients (groupe 2) étaient porteurs d’une cardiopathie ischémique sévère et n’étaient temporairement éligibles ni à une assistance ventriculaire gauche ni à une transplantation en urgence. Nous avons mesuré les variables hémodynamiques et métaboliques jusqu’à 96 heures après l’implantation du dispositif, ainsi que les défaillances de la pompe, la morbidité et la mortalité jusqu’à un an après l’implantation.
Résultats
Chez tous les patients le dispositif LP5.0 Impella a été placé sans complication par voie sous-clavière droite. La puissance cardiaque a augmenté de 0,64 (± 0,07) W à 0,94 (± 0,44) W et 1,02 (± 0,30) W à respectivement 24 et 72 heures. Le dispositif est resté en place pendant 12 (± 7,2) jours. Dans le groupe 1, cinq patients présentaient un Profil INTERMACS 3 au moment de l’insertion de la pompe. Trois ont pu être sevrés et ont survécu. Un patient, qui présentait un Profil INTERMACS 1, est décédé d’insuffisance cardiaque réfractaire en quelques heures. Dans le groupe 2, deux des trois patients ont bénéficié d’une transplantation cardiaque. Quatre patients ont présenté une hémorragie nécessitant au moins une transfusion, mais seulement un cas d’hémorragie a été causé directement par la pompe.
Conclusion
L’assistance ventriculaire gauche avec la pompe Impella LP5.0 semble être bien tolérée. Elle peut être particulièrement utile chez les patients présentant un infarctus aigu du myocarde compliqué de choc cardiogénique, qui atteignent un Profil INTERMACS 3 avec le traitement initial.
Background
In patients with acute myocardial infarction and cardiogenic shock, treatment is based on revisualization, inotropes, IABPs and respiratory support, in order to ensure haemodynamic stabilization and allow partial recovery of left ventricular systolic function. In some patients, the outcome can be uneventful with quick recovery and fast weaning from support. In other patients, mechanical assistance is needed within hours . These patients are described as Profile 1 in the INTERMACS classification . A third group includes patients who, after initial improvement, are ‘stuck’ in a stable but precarious haemodynamic status; they remain stable, with mid-level or high doses of intravenous inotropic agents and/or an IABP (INTERMACS Profiles 2 or 3).
In patients with INTERMACS Profiles 1 to 3, additional short-term left ventricular support can provide important benefits. In recent years, several short-term left ventricular devices have been developed. They are often associated with complications that limit their usefulness .
The Impella LP5.0 (Abiomed Europe GmbH, Aachen, Germany) pump appears especially interesting. Relatively light and easy to implement, it provides a theoretical output of 4 L/min while unloading the left ventricle. Moreover, we have shown that the Impella LP5.0 can be inserted through the subclavian artery, which allows mobilization of the patient .
We report on the feasibility and the safety of the Impella LP5.0 based on our experience of its use in nine patients with ischaemic cardiogenic shock.
Methods
Patients
From November 2002 to November 2008, nine medical patients (seven men, two women), mean (standard deviation [SD]) age 50 (14) years underwent implantation of an Impella LP5.0 in our institution as mechanical support for severe acute heart failure of ischaemic aetiology.
Six patients (group 1) presented with cardiogenic shock at the acute phase of an ST-segment elevation myocardial infarction and underwent primary or rescue angioplasty (P1–P6). All of these patients had inotropic support with dobutamine, an IABP and were under mechanical ventilation. Most were given epinephrine or norepinephrine ( n = 4).
Three patients (group 2) had severe ischaemic cardiomyopathy (P7–P9). The Impella LP5.0 was considered to allow further investigations or as a bridge to transplantation. These three patients were on inotropic support and had an IABP.
Impella LP5.0
The Impella LP5.0 consists of a rotor driven by an incorporated electrical motor and an inflow cannula ( Fig. 1 ). The pump is placed through the aortic valve in the left ventricle, and drives blood from the left ventricle to the ascending aorta through the inflow cannula. The performance of the pump depends on the rotary speed (up to 32.000 rpm) and the pressure it is subjected to (aortic pressure minus left ventricular pressure). This pressure difference is continuously registered through a pressure sensor located in front of the rotor. The pump flow in physiological conditions is around 4 L/min. Rotational speed is set at nine increasing levels on the driving console. In Europe, the device is approved for short-term use, for up to 10 days (CE marked). In all patients, the pump was inserted through the subclavian artery. This method has been described elsewhere . In brief, under general anaesthesia and heparinization, the right subclavian artery is exposed below the clavicle. An 8-mm vascular graft is sutured end-to-side and clamped closed to the anastomosis. A guidewire is introduced in the Impella LP5.0 pump through a specific lumen to the distal pigtail. The device is then introduced into the graft and an occluding plug around the 9-French driving cable is tied to prevent blood loss through the graft during the implantation manoeuvres. The guidewire and the pump are introduced into the subclavian artery to the left ventricle cavity, crossing the aortic valve, under fluoroscopic guidance or transoesophageal echocardiography. The correct position of the device is confirmed by fluoroscopy or transoesophageal echocardiography and the pressure signal at the console. The guidewire is then removed and the device is turned on. The graft around the cable is tied, closed to the anastomosis, cut off 1 cm further along, and removed. The surgical approach is closed and the driving cable with the sheath is allowed to exit from the subclavian wound. To remove the device, the same approach was used. Only the remaining graft is controlled; the ties around are removed and the device is gently pulled back and out. The graft is clamped and oversewn; then the surgical approach is closed.
Patient management
All patients had invasive arterial pressure monitoring. Five patients had a Swan Ganz catheter inserted just before Impella LP5.0 pump insertion. Patients were weaned from inotropic and vasopressor support as soon as possible. Filling volume was primarily triggered by the right atrial pressure and urine output. Organ perfusion was judged by clinical variables, urine output and evolution of blood lactate levels. The IABP remained in place until inotropic support was discontinued. Recovery of cardiac function was assessed by echocardiography. Angiotensin-converting enzyme inhibitors were introduced and their dose was increased as tolerated. Then low doses of beta-blocking agents were introduced. Weaning from the pump occurred over several days by reducing the pump speed from eight to two in 2–3 days.
Data collection and statistics
Patient data were collected retrospectively from the medical records. Patients were classified according to the INTERMACS classification. This agency defined seven clinical profiles to describe patients included in its ventricular assist device registry . These profiles provide convenient shorthand, which facilitates communication on the seriousness of acute heart failure and clarification of target populations for devices. Haemodynamic and laboratory data were collected before and up to 96 hours after Impella LP5.0 insertion. All causes of morbidity and mechanical failures were recorded. Acute renal failure was defined as urine output less than 30 mL/h. Mortality was recorded during hospitalisation, and at one month and one year postimplantation. Cardiac power output was measured as cardiac output times mean arterial pressure divided by 451 . Continuous data are presented as mean (SD).
Results
Patients
Clinical characteristics are presented in Table 1 . Mean age was 50.3 (14.0) years. The pump was inserted through the subclavian artery in all patients. In group 1, all but one patient were stabilized and relieved from shock but showed no sustained improvement These INTERMACS Profile 3 patients had the Impella LP5.0 implanted on a semi-urgent basis in the operating room. In one patient (P6), implantation occurred as a rescue operation in the catheterization laboratory after a failed primary percutaneous coronary intervention in an occluded left main artery.
| Group 1 | Group 2 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Patient | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Male sex | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
| Age (years) | 40 | 40 | 60 | 43 | 69 | 60 | 59 | 25 | 57 |
| AMI history | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
| INTERMACS Profile (24-hour) | P3 | P3 | P3 | P3 | P3 | P1 | P3 | P2 | P3 |
| Diabetes mellitus | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 |
| Occluded coronary artery | LM | LM | LM | LM | LAD | LAD-RCA | LM | RCA | LAD |
| TIMI flow grade | 3 | 2 | 2 | 3 | 3 | 1 | na | na | na |
| Systolic AP (mmHg) | 130 | 86 | 108 | 92 | 76 | 83 | 137 | 74 | 102 |
| Cardiac output (L/min) | 4.4 | 3.9 | 2.5 | 3 | 4.2 | 5.8 | na | 3.0 | na |
| Heart rate (beats/min) | 120 | 112 | 86 | 91 | 70 | 134 | 90 | 97 | 117 |
| IABP | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
| Dobutamine | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
| Milrinone | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
| Norepinephrine | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 1 |
| Epinephrine | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 |
| Mechanical ventilation | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 |
| Impella LP5.0 duration (days) | 10 | 23 | 18 | 17 | 10 | 2 | 1 | 13 | 14 |
| AMI to Impella LP5.0 delay (days) | 2 | 3 | 9 | 5 | 9 | 0 | na | na | na |
| GP IIb/IIIa antagonists | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | 0 |
| Clopidogrel | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | |
| Creatinine (μmol/L) | 105 | 88 | 289 | 212 | 206 | 235 | 148 | 119 | 85 |
| CRP (mg/L) | 89 | 286 | 22.2 | 203 | 233 | 22 | 124 | 34 | 46 |
| Arterial lactate (mmol/L) | 2.3 | 0.9 | 0.9 | 1.4 | 1.2 | 15.0 | 1.3 | 1.5 | 9.0 |
| pH | 7.51 | 7.3 | 7.38 | 7.42 | 7.48 | 7.05 | 7.47 | 7.49 | 7.49 |
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