Verschillende pulsgolven, Verschillende resultaten Defibrillation has remained largely unchanged since the 1960s. As a result the clinical performance of defibrillators is taken for granted. We tend to think that they all work the same. Biphasic technologies change the way we evaluate defibrillators. Instead of focusing on the size, shape, and weight of the box, we must now consider the therapeutic value delivered by each technology. The title of this presentation summarizes the two essential points we need to understand. First, in contrast to conventional monophasic defibrillation, biphasic technologies differ. Second, as a result of these technical differences clinical variation is expected, and seen, in the reported literature. De verschillen tussen de diverse bifasische technologieën

Defibrillatie Pulsgolven Pulsgolven tonen de electrische activiteit Stroom afgifte Tijd Stroomrichting Drie pulsgolven Monophasic Damped Sine Wave (MDS) Biphasic Truncated Exponential (BTE) Rectilinear Biphasic (RBW) Let’s start by taking a moment to understand the term “defibrillation waveform.” We can think of a waveform as a “prescription” for the electrical therapy. A waveform describes the amount of current delivered, the time over which it’s administered, and how it flows from the defibrillator. Three main waveforms are available for clinical use today. Let’s take a closer look at each.

Gedempte Sinus Golf (Damped Sine Wave) 30 jaar dezelfde Heeft hoge energie en stroomsterkte nodig Weinig effectief voor patiënten met een hoge transthoracale weerstand The Monophasic Damped Sine (MDS) wave had been, almost exclusively, used for external defibrillation since the 1960s. Its performance is greatly limited in patients with high transthoracic impedances. Escalating energy, aimed at raising the delivered current, is its only means for dealing with high patient impedance. Using energies ranging to 360 joules, monophasic defibrillators can deliver current levels that approach 60 amps. There is a growing body of evidence that shows high energy/current defibrillation produces post-shock myocardial dysfunction.

Bifasisch Gedempte Exponentieel Bifasic Truncated Exponential) De eerste generatie: Overgenomen van ICD applicaties met een lage weerstand Pulsgols verandert onder invloed van weerstand Many people consider this to be a first generation biphasic technology. It is known as a Biphasic Truncated Exponential (BTE) waveform. The energy is delivered in two phases. The first phase, seen as the positive waveform deflection, is indicative of current flow in one direction. The second, negative phase, indicates current flow in the reverse direction. Offering the promise of smaller size and extended battery life, the BTE waveforms were originally optimized for the low-impedance ICD application. Differing implementations of the BTE waveform have been adapted for external defibrillation by Physio-Control, Agilent Technologies, and others.

Rechtlijnige Bifasische Pulsgolf (Rectiliniair Bifasic Pulswave) Speciaal ontwikkelt voor extern gebruik: Constante stroom elimineert hoge piekstromen Vaste tijdsduur stabiliseert de pulsgolf ten opzichte van variërende weerstand The Rectilinear Biphasic waveform (RBW) represents the latest advance in biphasic technologies. In contrast to the BTE waveform, the RBW was developed specifically for external defibrillation. It sought to improve upon earlier biphasics by eliminating high peak currents, and delivering stability in the face of the high and varied impedance levels typically seen with transthoracic defibrillation. The RBW differs from the BTE waveform in two ways. Most notable is a constant current first phase of the RBW that reduces potentially harmful peak currents. Second is the stability of its shape in response to impedance. Both ZOLL Medical and GE Medical (formerly Marquette Electronics) Systems employ the Rectilinear Biphasic waveform.

Waar staan we vandaag: Wetenschappelijke gegevens Een vergelijking Experimentele Studies Onderzoek op “mensen” Een vergelijking Afgifte van de stroom Hoe gaan we met weerstand om Standpunten van de AHA To understand the clinical differences, we’ll look at biphasic technologies from three perspectives: First, we’ll review the scientific data. Early experimental studies showed the promise of biphasic defibrillation. The more recent clinical trials confirm its efficacy in humans. Next, we’ll do a functional comparison between the technologies. The growing body of clinical data permits us to delineate performance characteristics specific to each biphasic technology. Finally, we’ll look at biphasic technologies in light of the newest ACLS Guidelines.

Het Bifasische voordeel Experimentele studies tonen aan: Effect is afhankelijk van vorm pulsgolf Lagere defibrillatie drempel Minder functieverlies na de defibrillatie Early work in a variety of animal models consistently demonstrated that biphasic waveforms held much clinical promise. Perhaps most importantly for our purposes, the initial work told us the shape of the biphasic waveform dramatically influenced its ability to defibrillate. Next they found that biphasic waveforms required less current and lower energy to be effective. Finally, data is emerging that demonstrates lower energy biphasic shocks result in better post-shock myocardial function.

Effect is afhankelijk van de vorm van de pulsgolf ) Dixon et al. Circulation 1987;117:358-364. Defibrillation Threshold (Volts) 10M 2.5-7.5 3.5-6.5 5-5 6.5-3.5 7.5-2.5 50 100 150 200 250 300 (Canine) epicardial electrodes Waveform Shape (msec) These findings show us the influence of waveform shape on defibrillation efficacy. The horizontal axis presents six 10 millisecond waveforms. At the left, labeled “10M,” is a monophasic waveform. The remainder are differing biphasic waveforms. The vertical axis depicts the threshold of defibrillation (DFT). (On this graph, a lower value means it is easier to defibrillate). This study tells us two things: 1) As the shape of a biphasic waveform changes, so does its threshold for defibrillation (DFT). This has a direct bearing on clinical performance in that a lower DFT translates into higher efficacy at lower currents and energies. 2) Some biphasic waveforms, as illustrated by the second (2.5-7.5) and third (3.5-6.5) from the left, don’t work as well as monophasic waveforms.

Lagere Defibrillatie Drempel Sleutel factoren Monofasische DFT is verhoogd met 40% (p <0.05) Bifasische DFT blijft constant 120 80±30 100 80 54±19 DFT (J) 60 38±10 41±5 40 20 M B M B Conventional belief was that as an episode of VF lengthened, the threshold of defibrillation (DFT) rose. Practically speaking, this is another reason we escalated energies with monophasic defibrillators. This study shows us how biphasic defibrillation challenges that convention. It compared the performance of low-energy biphasic to high-energy monophasic shocks for extended-duration VF. It gives us important insight on why biphasic defibrillation requires less energy. Namely, the DFT for biphasic waveforms is lower, and more stable than that of monophasic. Initially we see a 30 percent lower DFT for the biphasic shocks following short-duration VF. When VF duration extends to 5 minutes the DFT for monophasic increases. However, with the biphasic technology we note that a long duration does not increase energy requirements. 10 sec 5 min Fibrillatie tijd Dierlijk hart 3 minuten zonder behandeling gevolgd door 2 minuten femoralis compressie Walcott et al. Circulation 1998; 98:2210-2215.

Minder functieverlies - 7 min VF Bifasische defibrillatie produceert minder functieverlies Gemiddelde arteriële druk hoger p<0.05 Defibrillation is not a benign event. While one might debate the occurrence of post-shock damage, there is an evolving body of data that demonstrates prolonged myocardial dysfunction. These data are from a landmark study that reported substantial post-shock cardiac dysfunction. The investigators examined various hemodynamic indices following both high-energy monophasic and low-energy biphasic shocks. They reported depression of both mean arterial pressure and ejection fraction 72 hours after delivery of high-energy shocks. Perhaps more significant than the values, are the recovery patterns exhibited. One notes immediate post-shock ejection fractions are depressed identically following both the high and low-energy shocks. Initially we see no difference to their recovery. However, at two hours post-shock the recovery patterns diverge. Whereas the ejection fractions approximated pre-shock levels at two hours for the animals shocked with the low-energy biphasic waveform, they continued to erode for those receiving the high-energy shocks. Data obtained 3 days later still showed lower ejection fractions associated with high energy shocks. Ejectie fractie hoger p<0.01 Studie in varkens Tang et al. Journal of American College of Cardiology, 1999;34:815-822.

Veel data door studies op “mensen” Klinische testen tonen aan: Efficiënt voor zowel VF & AF Voordeel van bifasisch defibrilleren neemt toe als VF langer bestaat Minder energie nodig In recent years human trials have overwhelmingly supported the advantages of biphasic defibrillation over conventional monophasic technology. The evidence continually demonstrates biphasic waveform technologies are, at the least, equal to monophasic, and require less energy.

Gepubliceerde Data betreft Lage Energie Patiënten vergelijk in diverse literatuur 912 Patiënten 1,2,3,4,5 0 Patiënten  200J This slide summarizes the cumulative research published on biphasic defibrillation. The initial 5 trials published in peer-reviewed scientific journals (through March 2001) collectively randomized more than 900 humans. Each of these prospective, multicenter trials compared the efficacy of a biphasic waveform to that of a monophasic waveform. All manufacturers have focused on studying lower energy biphasic shocks. One must note that data on the safety and efficacy of high-energy biphasic defibrillation (>200 joules) is absent from the peer-reviewed literature. > 200J 1 Brady et al. Circulation 1996;94:2507-2514. 2 Mittal et al. Journal of American College of Cardiology, 1999; 34:1595-1601. 3 Mittal et al. Circulation 2000;101:1282-1287. 4 Schneider et al. Circulation 2000;102:1780-1787. 5 Higgens et al. Prehospital Emergency Care 2000;4:305-313.

Agilent VF onderzoek BTE pulsgolf n = 316 p = ns Eerste schok effectivitieit This first trial randomized patients in the electrophysiology laboratory. Investigators reported equal first-shock efficacies for both a 200 joule monophasic damped sine and a 130 joule biphasic truncated exponential waveform. They also reported significantly less ST segment depression in the post-shock period following low energy biphasic shocks. Bardy et al. Circulation 1996;94:2507.

Medtronic VF onderzoek BTE pulsgolf p = ns Eerste schok effectivitieit A second trial with a different biphasic truncated exponential waveform also found no statistical difference in first-shock efficacy. In this study the investigators noted the failures with this particular low-energy biphasic to be associated with impedance levels above 88 ohms. Higgins, et al. Prehospital Emergency Care. 2000;4:305-313.

ZOLL VF onderzoek RBW pulsgolf 99% 93% Eerste schok effectivitieit In a similar fashion, the Rectilinear Biphasic waveform has been prospectively compared to a 200 joule monophasic shock in a multi-center randomized trial. For the first time, we see a low-energy biphasic shock outperform a high-energy monophasic shock. The single biphasic patient who not defibrillated on the first shock was successfully defibrillated at 150 joules. The patients who failed the initial monophasic shock required shocks up to 360 joules to successfully defibrillate. Mittal et al. Journal of American College of Cardiology, 1999; 34:1595-1601.

ZOLL (RBW) pulsgolf is Superieur voor moeilijke patiënten 99% 100% 100% p = 0.02 95% Defibrillatie resultaat 80% When the investigators separated the sample into high and low impedance groups an interesting finding emerged. Where as little difference is seen for the easy-to-defibrillate low-impedance patients, the Rectilinear Biphasic waveform demonstrated a very substantial improvement for the difficult, high-impedance patients. Investigators reported a 59 percent improvement in the first-shock success rate for those patients with transthoracic impedance in excess of 90 ohms. This finding suggests the Rectilinear Biphasic waveform excels where needed most. The manufacturer reports the FDA has cleared its claims of clinical superiority for the rectilinear biphasic waveform. 63% 60% <90 ohms >90 ohms 120J RBW 200J MDS Mittal et al. Journal of American College of Cardiology, 1999; 34:1595-1601.

“Out-of-Hospital” ervaringen Laatst geregistreerde ritme Belangrijkste conclusies 1 Alle patiënten kunnen bifasisch worden gedefibrilleerd 2 Aantoonbaar meer conversie in een georganiseerd ritme met de bifasische pulsgolf (P<0.0003) ~6.5 (1-17) minuten fibrillatiie 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Georganiseerd Asystole VF 55% N=210 93% N=129 This was one of the first large scale projects to examined low-energy biphasic in the out-of-hospital setting. It compared the efficacy of a three 150-joule shock biphasic protocol to the historic performance of standard monophasic defibrillation. Following an average of 6.5 minutes of VF, the investigators reported significantly more patients converted to an organized rhythm with the low energy biphasic defibrillator. Whereas 19% of the monophasic patients remained in VF, no biphasic patients failed to be defibrillated. 26% 19% 0% 7% MONO 200-360J BI 3 x 150J Gliner & White: Resuscitation 1999.

“Out-of-Hospital” ervaringen ORCA Trial (n=115) Vergelijk van 200-360J monofasische schokken met 150J bifasische schokken tijdens hartstilstand buiten het ziekenhuis Collaps tot eerste schok = 8.9 minuten Uitkomsten Monofasisch Bifasisch 1e schok succes 36/61 (59%) 52/54 (96%) p<0.0001 3e schok succes 42/61 (69%) 53/54 (98%) Totaal succes 49/58 (84%) 54/54 (100%) p=0.003 These are the latest findings from the prehospital setting. The study was a prospectively randomized trial that includes patients from four EMS systems. It compared traditional high-energy, monophasic defibrillation to a low-energy biphasic protocol of three 150 joule shocks. With a reported average of 8.9 minutes from collapse to first shock, the investigators reported 100% overall success for the low-energy biphasic shocks. This compared to 84% for the high-energy monophasic shocks. Upon examining the data closer, the trial showed low-energy biphasic to be better at all outcomes. Schneider et al. Circulation. 2000; 102:1780-1787.

Agilent AF onderzoek BTE pulsgolf p = ns The efficacy of a BTE waveform has also been evaluated for cardioverting atrial fibrillation. It outperformed the MDS technology at lower energies. However, it demonstrated a cumulative efficacy level equal to that of a high-energy monophasic. In fact, crossover data from this study suggested there to be an incremental benefit of a monophasic damped sine wave for atrial cardioversion when compared with a BTE technology. Page, et al. Circulation 2000; Supplement 102: II-574 (abstract).

ZOLL AF onderzoek Zoll RBW pulsgolf Willekeurig multicenter onderzoek n=165 Cardioversie Effectiviteit 0% 20% 40% 60% 80% 100% Monofasisch Rechtlijnig ZOLL Bifasisch 200 J 100 J 300 J 360 J 120 J 70 J 150 J 170J 68% 85% 91% 94% 21% 44% 79% p=0.005 p<0.0001 In contrast to the BTE technology, the Rectilinear Biphasic waveform has been reported to be superior for cardioverting atrial fibrillation for both first-shock and cumulative efficacies. In looking at these data you’ll note it took a 300 joule monophasic shock to equal the efficacy of a 70 joule Rectilinear Biphasic. Further, a 120 joule Rectilinear Biphasic shock was superior to the efficacy of a full-energy, 360 joule monophasic shock. Unsuccessful patients were crossed over to the maximum energy level of the opposite treatment arm. Fifty percent of the 16 patients who failed to convert with 360J monophasic were converted with a biphasic shock of 170J. No patient who failed with Rectilinear Biphasic shocks could be converted with 360J monophasic. Mittal et al. Circulation 2000; 101:1282-1287.

Zoll RBW - klinische ervaringen Eerste gegevens: 100% effectivieit voor 125 AF patiënten 85% werd geconverteerd met 50 joules 100% effectiviteit bij patiënten welke voorheen geconverteerd werden met 720J monophasic Electrophysiologists from the Cleveland Clinic reported the Rectilinear Biphasic technology to be the most effective means for cardioverting atrial fibrillation. In the largest series ever reported for biphasic defibrillation, 714 patients, the Rectilinear Biphasic technology was 99.8% effective for cardioverting AF. These patients were a continuation of an earlier series that reported 100% efficacy at an average of 67 joules. In examining a subset of eleven patients previously requiring dual-defibrillator (720J) shocks, they found the Rectilinear Biphasic to be 100% effective at an average of 137 joules. In verdere studies werd een succes percentage geconstateerd van 99,8% (713 of 714 patients) Niebauer MJ, et al. PACE 2000; 23: 605 (abstract). Niebauer, MJ, et al. Circulation. 2000 Supplement 102:II-574 (abstract).

Algemene conclusies Bifasische pulsgolven zijn effectief voor zowel VF als voor AF. Lage-energie BTE pulsgolven zijn klinisch gelijkwaardig t.o.v. de monofasische technologie. Lage-energie ZOLL RBW pulsgolven zijn klinisch superieur t.o.v. de monofasische technologie. Clearly human trials demonstrate that biphasic waveforms are effective for both defibrillation and cardioversion. The findings for first-generation, low-energy BTE waveforms generally report them to equal monophasic technology. On the other hand, the more recently developed Rectilinear Biphasic waveform demonstrates clinical superiority when compared to monophasic defibrillation. The varied findings lead us to the conclusion that biphasic waveforms differ.

Een functioneel vergelijk Verhouding tot weerstand Karakteristiek van stroomafgifte Klinische prestaties AHA gezichtspunten So you might ask, “Which is better?” From the start one must acknowledge that a direct clinical comparison between biphasic waveforms has yet to be done in a prospective, randomized trial. Nonetheless, the growing body of published, peer-reviewed human data does permit one to delineate technology specific performance characteristics. To do this we must examine the way biphasic technologies respond to impedance, resulting current delivery, trends in clinical literature, and performance in light of defined benchmarks.

“. . . De belangrijkste succes factor voor elektrische ventriculaire defibrillatie is het verkrijgen van voldoende stroomdichtheid. . .” 1 To understand the differences between biphasic technologies, we must take a moment to understand the importance of current. Although we select energy levels on a defibrillator, we must keep in mind it is the resulting delivered current that is responsible for defibrillating patients. 1 WA Tacker. Electrical Defibrillation. Boca Raton, Florida, CRC Press, Inc.; 1980 p14.

Volt Weerstand Stroom = De “Relatie” De Wet van Ohm . . . Als de weerstand toeneemt, moet het voltage ook toenemen om dezelfde hoeveelheid stroom over te brengen. This is Ohms Law. It explains the interaction of key factors involved with successful defibrillation. Voltage describes the volume of electricity stored when we charge the defibrillator. Impedance are those forces such as muscle, fat and air that resists the delivery of electricity to the heart. Current is the rate at which electricity flows from the paddle to the heart. Practically speaking, Ohms Law describes something that we intuitively accept. That is, in the face of high impedance we need to deliver more energy to insure adequate current is delivered.

Effect van patiënt weerstand bij bifasische pulsgolven Lage weerstand Hoge weerstand -20 10 20 30 40 50 4 8 12 -10 Eerste Generatie Bifasisch Biphasic waveforms most notably differ in their response to patient impedance. This slide shows the differing response of the BTE and RBW technologies. Upon examination one notes that the shape of the BTE waveform changes radically as higher patient impedance levels are encountered. Current levels fall and duration is increased in order to deliver the selected energy. Conversely, delivered current is consistent for the RBW. Recall, we noted earlier that clinical performance is tied to waveform shape. Variability in waveform duration and shape effects the defibrillation threshold, and ultimately, the clinical effectiveness. Rechtlijnig Bifasisch

De Stroom Paradox “Defibrillatie hangt af van de juiste energiekeuze zodat er voldoende transmyocardiale stroom ontwikkelt wordt teneinde defibrillatie te bewerkstelligen terwijl er op het- zelfde moment zo min mogelijk schade aan het hart ontstaat.” Current is a double-edge sword. While it is required for successful defibrillation, we know that too much is harmful. American Heart Association. Circulation. 2000:1029(suppl I):I-90-I-94.

Stroom bestaat uit 2 aspecten Piekstroom Hoogste stroomniveau dat tijdens de schok afgegeven wordt Wordt geassocieerd met myocard dysfunctie Gemiddelde stroom Gemiddelde stroomniveau dat tijdens de schok afgegeven wordt Bepalende factor van een succesvolle defibrillatie When referring to current, we need to understand it can be described two different ways. The peak current is the maximal current delivered by a shock. It is described by the high point of the defibrillation waveform. High peak currents are thought to be responsible for myocardial dysfunction. The average current, as its name implies, is the mean current delivered throughout the shock. By definition, it occurs somewhere below the peak for decaying waveforms such as the BTE.

Piekstroom per pulsgolf 43 35 15 10 20 30 40 RBW @ 120J Ampere BTE @ 130J Mono @ 200J 50 Monofasisch 200 Joules Bifasisch Standaard 150 Joules Rechtlijnig Bifasisch 120 Joules Stroom This slide provides a relative look at peak current delivery. The plot on the left is an overlay of the differing biphasic waveforms. On the right is a comparison of peak current delivery. While the peak current of the BTE waveform is somewhat lower than that of monophasic, the peak current of a RBW is 65% lower than that of monophasic. Tijd

Gemiddelde stroom - 150 Joules This slides demonstrates two key points. First, it shows the inverse relationship between current and impedance. That is for a given energy, 150 joules in this example, the average current delivered falls as the impedance rises. Second, we see how biphasic waveforms differ. At 150 joules, we see the RBW delivers a higher average current than does the BTE. Bron: ZOLL Medical Corporation

Gemiddelde stroom bij maximale energie When we compare the maximal energy setting of the RBW to the so-call “full-energy” BTE waveform we see these same two findings repeated. That is: 1) average current delivered falls in response to increased impedance, and 2) the averaged current delivered by a 200J RBW shock is greater than that of 360J BTE shock. One may think they are getting more effective current to the heart because the energy setting of one defibrillator is higher. But as we see here, with biphasic technologies that may not be true. Bron: ZOLL Medical Corporation

Op weg naar een wereld standaard Studies met 200J MDS als vergelijk 100% E 95% f f 90% i c 85% a In looking across independent studies one finds the various biphasic waveforms have all been compared to the same 200J monophasic waveform. Comparison to a common standard waveform can be useful for inferring differences among the various studies. When we contrast the results of these independent studies we should avoid looking at the absolute performance levels. Rather we should note how the biphasic shock compared to the monophasic standard in each study. Comparable protocols have produced varied results for the Typical Biphasic waveform of 200J or less. Only the Rectilinear Biphasic waveform has been demonstrated superiority to monophasic defibrillation. c 80% y 75% 200J MDS 130J BTE 200J MDS 130J BTE 200J MDS 120J RBW Medtronic1 Agilent2 ZOLL3 1 Higgens et al. Prehospital Emergency Care 2000;4:305-313. 2 Bardy GH, et al. Circulation. 1996; 94: 2507-2514. 3 Mittal S., et al. Journal of the American College of Cardiology. 1999; 34: 5.

Versus de AHA criteria Alleen de klinische prestaties van AHA statement uit 1997 aangaande bifasische pulsgolfen definieert drempels wanneer een pulsgolf superieur- of gelijkwaardig is. Alleen de klinische prestaties van De Rechtijnige Bifasische Pulsgolf overstijgen de superieure drempel. Finally, we need to examine the reported data in light of an AHA Scientific Statement. In 1997, the AHA’s Emergency Cardiac Care Committee published a statement that, in part, described a process for validating “alternative” defibrillation waveforms. In it, they described thresholds for equivalent and superior performance. Whereas the data published on BTE waveforms has achieved the equivalent threshold, only the data reported for the RBW technology crosses the threshold for superiority. American Heart Association. Automatic external defibrillators for public access defibrillation: recommendations for specifying and reporting arrhythmia analysis algorithm performance, incorporating new waveforms, and enhancing safety. Circulation. 1997; 95: 1677-1682.

Guidelines 2000 . . . Definiëren bifasisch energie niveau als  200 joules Definiëren geen bifasisch energie niveau hoger dan 200 joules Protocollen zijn pulsgolf specifiek Geeft klasse IIa aanbeveling aan bifasische schokken  200 joules While on the subject of the AHA, it is important to note that the most recent Guidelines for Resuscitation address biphasic defibrillation. Specifically, they define biphasic defibrillation as safe and effective at less than or equal to 200 joules. It is important to note, that in the absence on any high energy data, the AHA does not address shocks over 200 joules. Importantly, the Guidelines tell us biphasic protocols are waveform specific. That is, they need to be used in light of data from peer-reviewed, randomized trials. And finally they give low-energy biphasic defibrillation a Class IIa recommendation, the same classification as conventional monophasic defibrillation.

Samenvatting Bifasische pulsgolven verschillen Vorm Reactie op weerstand Stroom afgifte Klinische prestaties Bifasische pulsgolven zijn effectief voor externe defibrillatie Gelijkwaardige prestatie met minder energie Rechtlijnige bifasische pulsgolf : Een veelbelovende superieure prestatie In summary, biphasic defibrillation is here and is offers the promise of improved outcomes. There are differences in biphasic technologies and approaches. They need to be examined closely by clinicians.