Ann Thorac Surg 2005;79:1017-1022
© 2005 The Society of Thoracic Surgeons
New technology
Automatic Intraaortic Balloon Pump Timing Using an Intrabeat Dicrotic Notch Prediction Algorithm
Jan J. Schreuder, MD, PhDa,*,
Alessandro Castiglioni, MDa,
Andrea Donelli, MSa,
Francesco Maisano, MDa,
Jos R.C. Jansen, PhDb,
Ramzi Hanania, MSc,
Pat Hanlon, RNc,
Jan Bovelander, CRNAc,
Ottavio Alfieri, MDa,c
a Department of Cardiac Surgery, San Raffaele University Hospital, Milan, Italy
b Intensive Care, Leiden University Hospital, Leiden, the Netherlands
c Arrow International, Reading, Pennsylvania
Accepted for publication July 29, 2004.
* Address reprint requests to Dr Schreuder, Department of Cardiac Surgery, San Raffaele University Hospital, Via Olgettina 60, 20132 Milan, Italy (E-mail: schreuder{at}libero.it).
 |
Abstract
|
|---|
PURPOSE: The efficacy of intraaortic balloon counterpulsation (IABP) during arrhythmic episodes is questionable. A novel algorithm for intrabeat prediction of the dicrotic notch was used for real time IABP inflation timing control.
DESCRIPTION: A windkessel model algorithm was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was predicted using a percentage of calculated peak flow. Automatic inflation timing was set at intrabeat predicted dicrotic notch and was combined with automatic IAB deflation.
EVALUATION: Prophylactic IABP was applied in 27 patients with low ejection fraction (< 35%) undergoing cardiac surgery. Analysis of IABP at a 1:4 ratio revealed that IAB inflation occurred at a mean of 0.6 ± 5 ms from the dicrotic notch. In all patients accurate automatic timing at a 1:1 assist ratio was performed. Seventeen patients had episodes of severe arrhythmia, the novel IABP inflation algorithm accurately assisted 318 of 320 arrhythmic beats at a 1:1 ratio.
CONCLUSIONS: The novel real-time intrabeat IABP inflation timing algorithm performed accurately in all patients during both regular rhythms and severe arrhythmia, allowing fully automatic intrabeat IABP timing.
|
Introduction
|
|---|
| Dr Schreuder, Mr Hanania, Mr Bovelander, and Ms Hanlon disclose that they have a financial relationship with Arrow International; Dr Schreuder also has a financial relationship with CD Leycom.
|
Beneficial effects of intraaortic balloon pump (IABP) counterpulsation have been well demonstrated in various pathologies resulting in improved left ventricular (LV) performance [1–4]. However, the performance of current IABP devices during arrhythmia is suboptimal, resulting in inappropriate IABP timing with potentially negative hemodynamic effects [5, 6]. At the least, incorrect timing reduces the efficacy of IABP [7]. In a previous study it was demonstrated that premature IAB inflationSee page 872 markedly impaired LV ejection and relaxation by increasing LV afterload during the second part of the ejection phase, indicating that premature IAB inflation, which may occur during arrhythmia, can have detrimental effects on cardiac performance in heart failure patients [8]. Late IAB deflation resulted in increased stroke volume and increased stroke work due to afterload increase during early ejection followed by an afterload decrease in late ejection, demonstrating that incidental late IAB deflation will not negatively affect cardiac performance [8]. Arrhythmia commonly occurs in heart failure patients and is even more pronounced during cardiac surgery and interventional cardiology procedures. Within the first 4 days after cardiac surgery 30% of patients may manifest episodes of atrial fibrillation [9]. Given the changing acuity of the cardiac population and the increasing severity of irregular arrhythmia, alternative timing methods must be developed to optimize IABP hemodynamic support.
We developed an automatic IABP inflation timing using intrabeat dicrotic notch prediction (DNP) based on the windkessel model, where aortic flow is calculated from aortic pressure [10–12]. This method accurately detected and predicted the dicrotic notch in animal aortic pressure signals and in man aortic pressure signals with marked arrhythmia [11, 12]. Automated DNP-IABP inflation combined with R-wave or predictive deflation should provide accurate automatic timing control during both regular and irregular cardiac rhythms.
|
Patients and Methods
|
|---|
Patients
Twenty-seven consecutive patients, 49 to 74 years old, undergoing cardiac surgery and requiring prophylactic IABP were studied. Surgical procedures included left ventricular aneurysmectomy (n = 11, 9 with coronary artery bypass grafting), coronary artery bypass grafting (n = 10, 5 off-pump), and mitral valve repair (n = 6, 1 with coronary artery bypass grafting). Ejection fraction ranged from 13% to 35%, mean of 26% ± 6%. The hospital ethics committee approved the study and patients gave written informed consent.
Dicrotic Notch Prediction
The dicrotic notch detection algorithm has previously been described [10–12]. Briefly, a simplified windkessel model of the arterial tree was used to calculate real-time noncalibrated aortic flow from aortic pressure. We used fixed values for characteristic input impedance and arterial compliance [11, 12]. The dicrotic notch is detected at the first local minimum in the aortic flow signal after peak flow (Fig 1). The dicrotic notch is predicted by applying a preset percentage (20%) of maximal flow to the descending portion of the calculated flow, this setting predicted the dicrotic notch within 55 ± 4.4 ms during regular heart rate, sufficient to synchronize IAB inflation with aortic valve closure [12].
View larger version (37K):
[in this window]
[in a new window]
|
Fig 1. Examples of aortic pressure (Pao) and real-time derived aortic flow waveforms as calculated by the dicrotic notch prediction algorithm in 2 patients (A and B) with intraaortic balloon pump at 1:4 assist ratio.
|
|
Instrumentation
All patients received high-dose opioid anesthesia. The IAB catheters (Narrowflex LightWAVE; Arrow International, Reading, PA) were positioned through the femoral artery at 2-cm distal to the left subclavian artery. Fiberoptic micromanometer transducers were embedded in the tip of the IABs to measure aortic pressure (Pao), allowing accurate assessment of the dicrotic notch position in all patients [13].
The new DNP algorithm was implemented in a standard IABP device (ACAT-I; Arrow International). Upstroke pressure validation was achieved by a 15% limit of the pulse pressure of the previous beat. R-wave deflation or predictive deflation algorithms were used to achieve automatic deflation timing. The preferred deflation method was R wave deflation because it automatically adjusts the duration of IAB inflation to match the diastolic period. Whenever R-wave deflation induced a large increase in the end-diastolic aortic pressure or significantly compromised the systole following IABP deflation, the predictive method was used.
Electrocardiogram (ECG), Pao, and balloon pressure signals were digitally stored at a sampling rate of 250 Hz. In 5 patients LV pressure-volume (P-V) loops were measured, to verify the inflation and deflation timing, by a 7-Fr pressure-conductance catheter (CD Leycom, Zoetermeer, The Netherlands) and a P-V analyzer (Leycom CFL512; CD Leycom) [14].
Data Acquisition and Evaluation
The measurements were performed throughout the cardiac surgery, except during cardiopulmonary bypass, during episodes of regular and irregular heart rate, and also during off-pump coronary artery bypass. Data acquisition during regular heart rate at a 1:4 IABP assist ratio was used to locate the dicrotic notch during unassisted beats, which was compared with the inflation timing of the assisted beat (Fig 1). During arrhythmia, data were acquired at a 1:1 assist, from which heart rate (HR) and aortic pulse pressure (PP) were calculated.
|
Results
|
|---|
Off-line analysis was performed on data from 27 consecutive patients. All patients were discharged from the intensive care 1 to 5 days after cardiac surgery, without any IABP related complications.
Figure 1 illustrates two typical examples of aortic pressure (Pao) with corresponding aortic flow waveforms as calculated by the DNP algorithm. Accurate timing of inflation at the intrabeat predicted dicrotic notch can be observed in both examples. Table 1 presents inflation timing of 22 patients during 1:4 assist. Five patients were excluded due to persistent arrhythmia, precluding an accurate comparison. The HR (43–94) and PP range (22–88) of the unassisted beats indicate a wide variety of baseline conditions. The mean interval from peak systolic Pao to the dicrotic notch in the unassisted beats and the interval from peak systolic Pao to the pressure upstroke by the IABP, were almost identical, with a mean difference of 0.6 ± 5 ms and range of –11 to +12 ms. Thus the predictive value at 20% of the calculated peak aortic flow resulted in IAB inflation timing close to the actual dicrotic notch in all patients.
In all patients accurate, automatic timing at a 1:1 assist ratio could be performed during regular heart rate and arrhythmia. Figure 2 demonstrates two typical examples of left ventricular (LV) volume, LV pressure, Pao, and balloon pressure with LV P-V loops at 1:1 IABP assist during arrhythmia with DNP inflation and R-wave deflation. Accurate inflation timing is seen in both examples, whereas example B reveals late IAB deflation, defined as an increase in end-diastolic Pao. The P-V loops do not indicate evidence of very early IAB inflation, characterized by sharp increases in LV pressure during late ejection. In addition, no evidence of late deflation, characterized by increased LV pressure during early LV ejection is seen in both P-V loop examples. Table 2 presents HR and Pao characteristics during severe arrhythmia. No major arrhythmic episodes could be detected in 10 patients and consequently are not included in this table. Measured variability indicates extreme conditions, various types of arrhythmia (atrial fibrillation, premature ventricular contraction, ventricular tachycardia, and sinus bradycardia) with HR ranging from 31 to 208 bpm and aortic PP from 4 to 65 mm Hg. Of the 320 arrhythmic beats in 17 patients 2 beats were not assisted by the DNP-IABP. These non-IAB assisted beats were early extra-systolic beats generating pulse pressures below the 15% threshold value, needed to verify the Pao signal. Inflation set by DNP was accurate on all assisted beats. Automatic R-wave deflation was used in 21 of 27 patients (78%), providing optimal duration of the IAB assist. The remaining 6 patients (22%) required predictive deflation timing due to late IAB deflation, as depicted in example 2B of Figure 2.
View larger version (32K):
[in this window]
[in a new window]
|
Fig 2. Examples of IABP at 1:1 during arrhythmia in patient A (EF 25%) and B (EF 15%) undergoing mitral valve repair. Pressure (P) and volume (V) tracings show accurate automatic intrabeat IABP inflation without signs of too early IAB inflation in the left ventricular (lv) P-V plane. Automatic R-wave IAB deflation is correct in example A and too late in B, however without signs of afterload increase during early ejection in the P-V plane. (EF = ejection fraction; IABP = intraaortic balloon pump; Pao = mean aortic pressure; Piab = intraaortic balloon pressure; PLV = left ventricular pressure; VLV = left ventricular volume.)
|
|
Electrocautery did not impair the high-fidelity fiber-optic micro-manometer signal in any patient. During electrocautory deflation was performed using a pressure based predictive deflation algorithm. In all patients the fiberoptic pressure signal provided highly accurate, dynamic waveforms, where all landmarks were visible. Occasionally we observed small pressure artifacts around the last part of IAB deflation, probably due to catheter whip. In Figure 3 those small pressure artifacts can be observed (at the left in two early deflated IAB assists). Such minor pressure changes never affected the windkessel model.
View larger version (36K):
[in this window]
[in a new window]
|
Fig 3. Examples of (left) suboptimal and (right) optimal intraaortic balloon pump (IABP) assist in a patient (New York Heart Association functional class III, ejection fraction 15%, undergoing mitral valve reconstruction) during arrhythmia in the pressure-volume (P-V) plane. Although the IAB inflation timing is correct during suboptimal assist, as can be derived from the aortic pressure (Pao) tracing, the IAB inflation episodes are too short and three of nine beats were not assisted. During optimal assist the left ventricular (LV) afterload decreased and stroke volume increased with concomitant decreases in LV end-systolic and end-diastolic volume. (ECG = electrocardiogram; P/v = left ventricular pressure; PIAB = intraaortic balloon pressure; V/v = left ventricular volume.)
|
|
|
Comment
|
|---|
This study demonstrates, for the first time since the introduction of IABP, that accurate automatic closed-loop IABP timing was achieved using the intrabeat DNP algorithm for IAB inflation combined with automatic IAB deflation using R-wave or predicted deflation. The DNP algorithm generated immediate and precise inflation timing during both regular and arrhythmic periods. Extreme arrhythmia did not impair the DNP algorithm, which also was able to correctly assist in Pao waves with pulse pressures as low as 4 mm Hg. Left ventricular pressure-volume loops confirmed accurate inflation timing.
R-wave deflation was effective in 78% of patients, inducing end-diastolic Pao decrease. In the remaining patients predictive IAB inflation was used. However, Kern and colleagues [4] reported in a clinical IABP study that IAB deflation might be performed late in diastole without adverse hemodynamic effects, which is confirmed in example B of Figure 2, indicating elevated end-diastolic Pao due to late IAB deflation without an elevated LV pressure during early ejection suggests no impairment in the LV P-V plane. In a previous study we demonstrated that late IAB deflation resulted in increased SV and increased SW by afterload increase during early ejection and afterload decrease in late ejection, indicating that incidental late IAB deflation will not negatively affect cardiac performance [8].
Previous attempts have been made to develop algorithms that are suitable during arrhythmia [5, 6]. Sakamoto and coworkers [5], tested a timing algorithm during atrial fibrillation, however their method required reliable dicrotic notch detection, which was not available. Kantrowitz and associates [7] conducted a feasibility study in 10 patients using an undefined closed-loop IABP device. The device required between 7 to 20 seconds to optimize timing, suggesting that during severe arrhythmia timing variability may occur.
The applied fiberoptic pressure signal provided aortic pressure waveforms at high-time resolution during 20 to 48 hours of IABP, necessary for accurate flow calculations, and was not influenced by electrocautory [13].
Intraaortic balloon pump has shown to stabilize medically refractory ventricular arrhythmia [15]. Methods, such as the DNP algorithm, which are capable of providing intrabeat beat adjustment in timing, may provide optimal assist under a wide range of patient conditions and may markedly increase the therapeutic effectiveness of IABP in clinical practice. This is illustrated in Figure 3, revealing the effects of suboptimal IABP assist and optimal IABP assist in a patient (New York Heart Association functional class III, ejection fraction 15%, undergoing mitral valve reconstruction) during arrhythmia. Although the IAB inflation timing is correct (using the DNP method) during suboptimal assist, the IAB inflation episodes were too short and three of nine beats were not assisted. During optimal assist of each cardiac cycle (performed immediately after the suboptimal assist) LV afterload decreased and stroke volume increased with concomitant decreases in LV end-systolic and end-diastolic volume. Another possible advantage of automatic closed-loop control is a reduction of operator-dependent timing errors in IABP.
The number of patients included in this study was relatively small, however, when combined with the preclinical phase of the study the arterial pressure waves from 62 patients with diverse arrhythmia has been analyzed [11, 12]. Although all patients recordings demonstrated remarkable accuracy of inflation timing using the DNP algorithm in a wide variety of cardiac arrhythmia's and hemodynamic conditions, it is still possible that the novel DNP algorithm was not exposed to all possible conditions which may be encountered in the clinical environment.
|
Conclusion
|
|---|
The present study demonstrates that the novel real-time intrabeat IABP inflation-timing algorithm performed accurately in all patients during both regular rhythms and severe arrhythmia, allowing fully automatic IABP timing.
|
Disclosures and Freedom of Investigation
|
|---|
This study was funded by the Department of Cardiac Surgery, San Raffaele University Hospital (Milan, Italy) and Arrow International (Reading, PA). Doctor Schreuder serves as a consultant for Arrow International and CD Leycom. The tested technology was borrowed to conduct the study. The authors state that they had full control of the design of the study, methods used, outcome parameters, analysis of data, and production of the written report.
|
Footnotes
|
|---|
Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
|
References
|
|---|
- Kantrowitz A, Kantrowitz A. Experimental augmentation of coronary flow by retardation of arterial pressure pulse Surgery 1953;34:678.[Medline]
- Willerson J, Curry G, Watson J, et al. Intraaortic balloon counterpulsation in patients in cardiogenic shock, medically refractory left ventricular failure and/or recurrent ventricular tachycardia Am J Med 1975;58:183-191.[Medline]
- Nichols AB, Pohost GM, Gold HK, et al. Left ventricular function during intra-aortic balloon pumping assessed by multigated cardiac blood pool imaging Circulation 1978;58(Suppl 1):176-183.
- Kern MJ, Aguirre FV, Caracciolo EA, et al. Hemodynamic effects of new intra-aortic balloon counterpulsation timing methods in patients: a multicenter evaluation Am Heart J 1999;137:1129-1136.[Medline]
- Sakamoto T, Arai H, Maruyama T, Suzuki A. New algorithm of intra-aortic balloon pumping in patients with atrial fibrillation ASAIO J 1995;41:79-83.[Medline]
- Kantrowitz A, Freed PS, Cardona RR, et al. Initial clinical trial of a closed loop, fully automatic intra-aortic balloon pump ASAIO J 1992;38:M617-M621.[Medline]
- Kantrowitz A, Cardona RR, Freed PS. Percutaneous intra-aortic balloon counterpulsation Crit Care Clin 1992;8:819-837.[Medline]
- Schreuder JJ, Maisano F, Donelli A, et al. Beat-to-beat effects of intraaortic balloon pump timing on left ventricular performance in patients with low ejection fraction. Ann Thorac Surg 2005;79:872–80..
- Greengurg M, Katz N, Juliano S, et al. Atrial pacing for the prevention of atrial fibrillation after cardiovascular surgery J Am Coll Cardiol 2000;35:1416-1422.[Abstract/Free Full Text]
- Wesseling KH, Jansen JRC, Settels JJ, Schreuder JJ. Computation of aortic flow from pressure in humans using a nonlinear, three-element model J Applied Physiol 1993;74:2566-2573.[Abstract/Free Full Text]
- Hoeksel SAAP, Jansen JRC, Blom JA, Schreuder JJ. Detection of dicrotic notch in arterial pressure signals J Clin Monit 1997;13:309-316.[Medline]
- Donelli A, Jansen JRC, Hoeksel B, et al. Performance of a real-time dicrotic notch prediction algorithm in arrhythmic human aortic pressure signals J Clin Monit 2002;17:181-185.
- Reesink KD, Van der Nagel T, Bovelander J, Jansen JRC, van der Veen FH, Schreuder JJ. Feasibility of a fiber-optic system for invasive blood pressure measurements Cathet Cardiovasc Intervent 2002;57:272-276.[Medline]
- Schreuder JJ, Steendijk P, van der Veen FH, et al. Acute and short-term effects of partial left ventriculectomy in dilated cardiomyopathy: Assessment by pressure-volume loops J Am Coll Cardiol 2000;36:2104-2114.[Abstract/Free Full Text]
- Fotopoulos GD, Mason MJ, Walker S, et al. Stabilization of medically refractory ventricular arrhythmia by intra-aortic balloon counter pulsation Heart 1999;82:96-100.[Abstract/Free Full Text]
Related Articles
-
INVITED COMMENTARY
- William L. Holman
Ann. Thorac. Surg. 2005 79: 1022.
[Extract]
[Full Text]
[PDF]
-
Beat-to-Beat Effects of Intraaortic Balloon Pump Timing on Left Ventricular Performance in Patients With Low Ejection Fraction
- Jan J. Schreuder, Francesco Maisano, Andrea Donelli, Jos R.C. Jansen, Pat Hanlon, Jan Bovelander, and Ottavio Alfieri
Ann. Thorac. Surg. 2005 79: 872-880.
[Abstract]
[Full Text]
[PDF]
Top
Abstract
Introduction
