Coronary angiographic findings for out-of-hospital cardiac arrest survivors presenting with nonshockable rhythms and no ST elevation post resuscitation.

BACKGROUND: Recent guidelines suggest that coronary angiography (CAG) should be considered for out-of-hospital cardiac arrest (OHCA) survivors, including those without ST elevation (STE) and without shockable rhythms. However, there is no prospective data to support CAG for survivors with nonshockable rhythms and no STE post resuscitation. METHODS: This was a re-analysis of the PEARL study (randomized OHCA survivors without STE to early CAG versus not). Patients were subdivided by initial rhythm as nonshockable (Nsh) vs shockable (Sh). The primary outcome was coronary angiographic evidence of acute culprit lesion, with secondary outcomes being survival to hospital discharge and neurological recovery. RESULTS: The PEARL study included 99 patients with OHCA from a presumed cardiac etiology, 24 with nonshockable and 75 with shockable rhythms. There was no difference in the frequency of CAG between the two groups [71% (Nsh) and 75% (Sh); p = 0.79], presence of CAD [81% (Nsh) and 68% (sh); p = 0.37, or culprit lesions identified in each group [50% (Nsh) and 45% (Sh); p = 0.78. Nonshockable patients had worse discharge survival [33% (Nsh) vs 57% (Sh); p = 0.04] and those survived, had worse neurological recovery [30% (Nsh) vs 54% (Sh); p = 0.02] compared to shockable patients. CONCLUSIONS: OHCA survivors presenting with nonshockable rhythms and no STE post resuscitation had similar prevalence of culprit coronary lesions to those with shockable rhythms. CAG may be considered in patients with OHCA without STE regardless of initial presenting rhythm. There was no benefit of emergent CAG both in shockable and non-shockable rhythms.

A local neighborhood volunteer network improves response times for simulated cardiac arrest.

AIM: Each minute is crucial in the treatment of out-of-hospital cardiac arrest (CA). Immediate chest compressions and early defibrillation are keys to good outcomes. We hypothesized that a coordinated effort of alerting trained local neighborhood volunteers (vols) simultaneously with 911 activation of professional EMS providers would result in substantial decreases in call-to-arrival times, leading to earlier CPR and defibrillation. METHODS: We developed a program of simultaneously alerting CPR- and AED-trained neighborhood vols and the local EMS system for CA events in a retirement residential neighborhood in Southern Arizona, encompassing approximately 440 homes. The closest EMS station is 3.3 miles from this neighborhood. Within this neighborhood, 15 vols and the closest EMS station were involved in multiple days of mock CA notifications and responses. RESULTS: The two groups differed significantly in distance to the mock CA event and in response times. The volunteers averaged 0.3 ±â€¯0.2 miles from the mock CA incidences while the closest EMS station averaged 3.4 ±â€¯0.1 miles away (p < 0.0001). Response times (time from call to arrival) also differed. Two volunteers, one bringing an AED, averaged 1 min 38 s ±â€¯53 s in Phase 1, while it took the EMS service an average of 7 min 20 s ±â€¯1 min 13 s to arrive on scene; p < 0.0001. CONCLUSION: Local neighborhood volunteers were geographically closer and arrived significantly sooner at the mock CA scene than did the EMS service. The approximate time savings from call to arrival with the volunteers was 4-6 min.

"All citizens of the world can save a life" - The World Restart a Heart (WRAH) initiative starts in 2018.

"All citizens of the world can save a life". With these words, the International Liaison Committee on Resuscitation (ILCOR) is launching the first global initiative - World Restart a Heart (WRAH) - to increase public awareness and therefore the rates of bystander cardiopulmonary resuscitation (CPR) for victims of cardiac arrest. In most of the cases, it takes too long for the emergency services to arrive on scene after the victim's collapse. Thus, the most effective way to increase survival and favourable outcome in cardiac arrest by two- to fourfold is early CPR by lay bystanders and by "first responders". Lay bystander resuscitation rates, however, differ significantly across the world, ranging from 5 to 80%. If all countries could have high lay bystander resuscitation rates, this would help to save hundreds of thousands of lives every year. In order to achieve this goal, all seven ILCOR councils have agreed to participate in WRAH 2018. Besides schoolchildren education in CPR ("KIDS SAVE LIVES"), many other initiatives have already been developed in different parts of the world. ILCOR is keen for the WRAH initiative to be as inclusive as possible, and that it should happen every year on 16 October or as close to that day as possible. Besides recommending CPR training for children and adults, it is hoped that a unified global message will enable our policy makers to take action to address the inequalities in patient survival around the world.

"Bystander" chest compressions and assisted ventilation independently improve outcome from piglet asphyxial pulseless "cardiac arrest".

BACKGROUND: Bystander cardiopulmonary resuscitation (CPR) without assisted ventilation may be as effective as CPR with assisted ventilation for ventricular fibrillatory cardiac arrests. However, chest compressions alone or ventilation alone is not effective for complete asphyxial cardiac arrests (loss of aortic pulsations). The objective of this investigation was to determine whether these techniques can independently improve outcome at an earlier stage of the asphyxial process. METHODS AND RESULTS: After induction of anesthesia, 40 piglets (11.5+/-0.3 kg) underwent endotracheal tube clamping (6.8+/-0.3 minutes) until simulated pulselessness, defined as aortic systolic pressure <50 mm Hg. For the 8-minute "bystander CPR" period, animals were randomly assigned to chest compressions and assisted ventilation (CC+V), chest compressions only (CC), assisted ventilation only (V), or no bystander CPR (control group). Return of spontaneous circulation occurred during the first 2 minutes of bystander CPR in 10 of 10 CC+V piglets, 6 of 10 V piglets, 4 of 10 CC piglets, and none of the controls (CC+V or V versus controls, P<0.01; CC+V versus CC and V combined, P=0.01). During the first minute of CPR, arterial and mixed venous blood gases were superior in the 3 experimental groups compared with the controls. Twenty-four-hour survival was similarly superior in the 3 experimental groups compared with the controls (8 of 10, 6 of 10, 5 of 10, and 0 of 10, P<0.05 each). CONCLUSIONS: Bystander CPR with CC+V improves outcome in the early stages of apparent pulseless asphyxial cardiac arrest. In addition, this study establishes that bystander CPR with CC or V can independently improve outcome.

Endothelin-1 vasoconstriction during swine cardiopulmonary resuscitation improves coronary perfusion pressures but worsens postresuscitation outcome.

BACKGROUND: Vasoconstriction during cardiopulmonary resuscitation (CPR) improves coronary perfusion pressure (CPP) and thereby outcome. The combination of endothelin-1 (ET-1) plus epinephrine improved CPP during CPR compared with epinephrine alone in a canine cardiac arrest model. The effect of the combination on outcome variables, such as successful resuscitation and survival, has not been investigated. METHODS AND RESULTS: Twenty-seven swine were randomly provided with 1 mg epinephrine (Epi group) or 1 mg epinephrine plus 0.1 mg ET-1 (ET-1 group) during a prolonged ventricular fibrillatory cardiac arrest. ET-1 resulted in substantially superior aortic relaxation pressure and CPP during CPR. These hemodynamic improvements tended to increase initial rates of restoration of spontaneous circulation (8 of 10 versus 8 of 17, P=0.12). However, continued intense vasoconstriction from ET-1 led to higher aortic diastolic pressure and very narrow pulse pressure after resuscitation. The mean pulse pressure 1 hour after resuscitation was 7+/-8 mm Hg with ET-1 versus 24+/-1 mm Hg with Epi, P<0.01. Most importantly, the postresuscitation mortality was dramatically higher in the ET-1 group (6 of 8 versus 0 of 8 in the Epi group, P<0.01). CONCLUSIONS: These data establish that administration of ET-1 during CPR can result in worse postresuscitation outcome. The intense vasoconstriction from ET-1 improved CPP during CPR but had detrimental effects in the postresuscitation period.

Adverse hemodynamic effects of interrupting chest compressions for rescue breathing during cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest.

BACKGROUND: Despite improving arterial oxygen saturation and pH, bystander cardiopulmonary resuscitation (CPR) with chest compressions plus rescue breathing (CC+RB) has not improved survival from ventricular fibrillation (VF) compared with chest compressions alone (CC) in numerous animal models and 2 clinical investigations. METHODS AND RESULTS: After 3 minutes of untreated VF, 14 swine (32+/-1 kg) were randomly assigned to receive CC+RB or CC for 12 minutes, followed by advanced cardiac life support. All 14 animals survived 24 hours, 13 with good neurological outcome. For the CC+RB group, the aortic relaxation pressures routinely decreased during the 2 rescue breaths. Therefore, the mean coronary perfusion pressure of the first 2 compressions in each compression cycle was lower than those of the final 2 compressions (14+/-1 versus 21+/-2 mm Hg, P<0.001). During each minute of CPR, the number of chest compressions was also lower in the CC+RB group (62+/-1 versus 92+/-1 compressions, P<0.001). Consequently, the integrated coronary perfusion pressure was lower with CC+RB during each minute of CPR (P<0.05 for the first 8 minutes). Moreover, at 2 to 5 minutes of CPR, the median left ventricular blood flow by fluorescent microsphere technique was 60 mL. 100 g(-1). min(-1) with CC+RB versus 96 mL. 100 g(-1). min(-1) with CC, P<0.05. Because the arterial oxygen saturation was higher with CC+RB, the left ventricular myocardial oxygen delivery did not differ. CONCLUSIONS: Interrupting chest compressions for rescue breathing can adversely affect hemodynamics during CPR for VF.

Myocardial dysfunction after resuscitation from cardiac arrest: an example of global myocardial stunning.

OBJECTIVES: This study investigated the effect of prolonged cardiac arrest and subsequent cardiopulmonary resuscitation on left ventricular systolic and diastolic function. BACKGROUND: Cardiac arrest from ventricular fibrillation results in cessation of forward blood flow, including myocardial blood flow. During cardiopulmonary resuscitation, myocardial blood flow remains suboptimal. Once the heart is defibrillated and successful resuscitation achieved, reversible myocardial dysfunction, or "stunning," may occur. The magnitude and time course of myocardial stunning from cardiac arrest is unknown. METHODS: Twenty-eight domestic swine (26 +/- 1 kg) were studied with both invasive and noninvasive measurements of ventricular function before and after 10 or 15 min of untreated cardiac arrest. Contrast left ventriculograms, ventricular pressures, cardiac output, isovolumetric relaxation time (tau) and transthoracic Doppler-echocardiographic studies were obtained. RESULTS: Twenty-three of 28 animals were successfully resuscitated and postresuscitation data obtained. Left ventricular ejection fraction showed a significant reduction 30 min after resuscitation (p < 0.05). Regional wall motion analysis revealed diffuse, global left ventricular systolic dysfunction. Left ventricular end-diastolic pressure increased significantly in the postresuscitation period (p < 0.05). Isovolumetric relaxation time (tau) was significantly increased over baseline by 2 h after resuscitation (p < 0.05). Similar findings were noted with the Doppler-echocardiographic analysis, including a reduction in fractional shortening (p < 0.05), a reduction in mitral valve deceleration time (p < 0.05) and an increase in left ventricular isovolumetric relaxation time at 5 h after resuscitation (p < 0.05> By 24 h, these invasive and noninvasive variables of systolic and diastolic left ventricular function had begun to improve. At 48 h, all measures of left ventricular function had returned to baseline levels. CONCLUSIONS: Myocardial systolic and diastolic dysfunction is severe after 10 to 15 min of untreated cardiac arrest and successful resuscitation. Full recovery of this postresuscitation myocardial stunning is seen by 48 h in this experimental model of ventricular fibrillation cardiac arrest.

Importance of the duration of inadequate coronary perfusion pressure on resuscitation from cardiac arrest.

The effect of the duration of inadequate coronary perfusion pressure on resuscitation from cardiac arrest was examined in 32 mongrel dogs with a mean weight of 22 +/- 5 kg. In all dogs, the heart was electrically fibrillated and closed chest compression with assisted ventilation was performed for 15 minutes. At this time, all dogs had an inadequate coronary perfusion pressure (mean 7 +/- 9 mm Hg) and were randomized to a control group (group 1) with continued closed chest compression or to one of the three groups with open chest cardiac massage. These three groups differed only in the duration of continued closed chest compression before initiation of open chest massage (15, 20 and 25 minutes, respectively, in groups 2, 3 and 4). The control group (group 1) had no significant increase in coronary perfusion pressure, and only one of the eight dogs could be resuscitated. The three groups with open chest cardiac massage had a significant increase in coronary perfusion pressure (from 5 +/- 9 to 51 +/- 26 mm Hg, p less than 0.05), but the rate of successful resuscitation depended on the duration of inadequate coronary perfusion pressure before cardiac open chest massage. In group 2, six of eight dogs were resuscitated (p less than 0.05 compared with the control group); in group 3, three of eight dogs were resuscitated and in group 4 none of the eight dogs was resuscitated. The resuscitation rate was significantly (p less than 0.05) greater in group 2 than in group 4. These findings indicate that techniques that improve coronary perfusion pressure during cardiopulmonary resuscitation must be applied before extensive myocardial cellular dysfunction occurs if the probability of successful resuscitation is to be improved.

Bedside cardiovascular examination in patients with severe chronic heart failure: importance of rest or inducible jugular venous distension.

OBJECTIVES: The aim of this study was to determine the sensitivity, specificity and utility of the cardiovascular examination in predicting cardiac hemodynamics in patients with advanced chronic congestive heart failure. BACKGROUND: Although the physical signs of acute left heart failure have been shown to correlate relatively well with cardiac hemodynamics, their reliability in estimating hemodynamics in patients with chronic heart failure has recently been questioned. METHODS: We prospectively recorded the history, cardiovascular physical signs present at bedside examination and the hemodynamic measurements obtained at right heart catheterization in 52 patients with chronic congestive heart failure undergoing in-hospital evaluation for possible heart transplantation. In addition, we obtained chest radiographs and multigated nuclear scans for the evaluation of left ventricular function. RESULTS: Pulmonary rales, a left ventricular third heart sound, jugular venous distension and the abdominojugular test, when positive, indicated higher right heart pressures and lower measures of cardiac performance. The presence of jugular venous distension, at rest or inducible, had the best combination of sensitivity (81%), specificity (80%) and predictive accuracy (81%) for elevation of the pulmonary capillary wedge pressure (> or = 18 mm Hg). Furthermore, in this population sample, the probability of an elevated wedge pressure was 0.86 when either variable was present. CONCLUSIONS: The bedside cardiovascular examination in the patient with chronic heart failure is extremely useful in identifying patients with elevation of right and left heart pressures. Examination for jugular venous distension at rest or by the abdominojugular test is simple and highly sensitive and specific in assessing left heart pressures in these patients.

Twenty-four hour survival in a canine model of cardiac arrest comparing three methods of manual cardiopulmonary resuscitation.

Two new modifications of manual cardiopulmonary resuscitation, high impulse compression at a rate of 120/min and interposed abdominal compression at a rate of 60/min, have been reported to produce better hemodynamic responses than standard cardiopulmonary resuscitation at 60/min. However, the effect of these two new methods on initial resuscitation success and 24 hour survival is unknown. In this study, 30 mongrel dogs were divided into three equal groups, each treated with one of three types of manual cardiopulmonary resuscitation. Ventricular fibrillation was induced electrically in morphinized, endotracheally intubated dogs emerging from halothane anesthesia. After 3 minutes of circulatory arrest without intervention, one of the three techniques of manual cardiopulmonary resuscitation was begun, and continued for 17 minutes. Defibrillation was performed at 20 minutes. Successful resuscitation was defined as a mean arterial blood pressure of at least 60 mm Hg, without chest compressions, 10 minutes after the initial defibrillation attempt. Intensive care was provided for 2 hours, including hemodynamic and respiratory monitoring, and drug intervention when required. Twenty-four hour survival and neurologic deficit were used as critical measures of outcome. Ten of 30 animals survived 24 hours with a mean neurologic deficit score of 5% (normal = 0, brain dead = 100). There was no difference in initial resuscitation success, 24 hour survival or neurologic deficit of the survivors among the three manual cardiopulmonary resuscitation methods. Aortic diastolic and calculated coronary perfusion pressures were similar for all three methods. Well performed standard manual cardiopulmonary resuscitation is as effective as these modified versions (high impulse compression and interposed abdominal compression) when compared in the same animal model.

Changes in expired end-tidal carbon dioxide during cardiopulmonary resuscitation in dogs: a prognostic guide for resuscitation efforts.

Expired end-tidal carbon dioxide (PCO2) measurements made during cardiopulmonary resuscitation have correlated with cardiac output and coronary perfusion pressure when wide ranges of blood flow are included. The utility of such measurements for predicting resuscitation outcome during the low flow state associated with closed chest cardiopulmonary resuscitation remains uncertain. Expired end-tidal PCO2 and coronary perfusion pressures were measured in 15 mongrel dogs undergoing 15 min of closed chest cardiopulmonary resuscitation after a 3 min period of untreated ventricular fibrillation. In six successfully resuscitated dogs, the mean expired end-tidal PCO2 was significantly higher than that in nine nonresuscitated dogs only after 14 min of cardiopulmonary resuscitation (6.2 +/- 1.2 versus 3.4 +/- 0.8 mm Hg; p less than 0.05). No differences in expired end-tidal PCO2 values were found at 2, 7 or 12 min of cardiopulmonary resuscitation. A significant decline in end-tidal PCO2 levels during the resuscitation effort was seen in the nonresuscitated group (from 6.3 +/- 0.8 to 3.4 +/- 0.8 mm Hg; p less than 0.05); the successfully resuscitated group had constant PCO2 levels throughout the 15 min of cardiac arrest (from 6.8 +/- 1.1 to 6.2 +/- 1.2 mm Hg). Changes in expired PCO2 levels during cardiopulmonary resuscitation may be a useful noninvasive predictor of successful resuscitation and survival from cardiac arrest.

A study of chest compression rates during cardiopulmonary resuscitation in humans. The importance of rate-directed chest compressions.

A prospective, cross-over trial was performed comparing two different rates of precordial compression using end-tidal carbon dioxide as an indicator of the efficacy of cardiopulmonary resuscitation in 23 adult patients. A second purpose of this study was to determine the effect of audio-prompted, rate-directed chest compressions on the end-tidal carbon dioxide concentrations during cardiopulmonary resuscitation. Patients with cardiac arrest received external chest compressions, initially in the usual fashion without rate direction and then with rhythmic audiotones for rate direction at either 80 compressions per minute or 120 compressions per minute. Nineteen of 23 patients had higher end-tidal carbon dioxide levels at the compression rate of 120 per minute. The mean end-tidal carbon dioxide level during compressions of 120 per minute was 15.0 +/- 1.8 mm Hg, slightly but significantly higher than the mean level of 13.0 +/- 1.8 mm Hg at a compression rate of 80 per minute. However, end-tidal carbon dioxide levels increased rather dramatically when audiotones were used to guide the rate of chest compressions. Mean end-tidal carbon dioxide concentration was 8.7 +/- 1.2 mm Hg during standard cardiopulmonary resuscitation immediately before audio-prompted, rate-directed chest compression and increased to 14.0 +/- 1.3 mm Hg after the first 60 seconds of audible tones directing compressions. Using end-tidal carbon dioxide as an indicator of cardiopulmonary resuscitation efficacy, we conclude that audible rate guidance during chest compressions may improve cardiopulmonary resuscitation performance.

Bystander cardiopulmonary resuscitation. Concerns about mouth-to-mouth contact.

BACKGROUND: Bystander cardiopulmonary resuscitation (CPR) is performed on only a small percentage of patients who suffer cardiac arrest. We conducted a study to elucidate attitudes toward and potential obstacles to performance of bystander CPR. METHODS: Attitude survey of 975 people on the University Heart Center, University of Arizona, Tucson, mailing list. Participants were asked about their willingness to perform CPR under four conditions, with varying relationships (stranger vs relative or friend) and CPR techniques (chest compressions plus mouth-to-mouth ventilation [CC+V] vs chest compressions alone [CC]). RESULTS: Participants rated willingness to perform CPR and concern about disease transmission. Both relationship and CPR technique affected willingness to respond. Only 15% would "definitely" provide CC+V with strangers compared with 68% who would "definitely" perform CC. Even with relatives or friends, only 74% would "definitely" provide CC+V compared with 88% who would "definitely" provide CC. Eighty-two percent of participants were at least "moderately" concerned about disease transmission. CONCLUSION: Concerns regarding mouth-to-mouth ventilation appear to create substantial barriers to performance of bystander CPR. Intensified educational efforts and investigations of new approaches to bystander CPR are warranted.

Changes in right ventricular relaxation during acute anterior myocardial infarction in pigs.

To determine the effect of an anteroseptal myocardial infarction on right ventricular systolic and diastolic function, we studied 12 pigs before and 1 h after left anterior descending coronary artery occlusion. Total arterial occlusion was achieved by the percutaneous, transcatheter placement of a 1 mm Teflon plug into the mid portion of the artery. The resulting infarction involved 28 (SEM 3)% of the left ventricular wall, in the anterior and septal regions. A small rim of the right ventricular free wall adjacent to the septum and the right ventricular apex were also affected. End diastolic pressures in both ventricles rose significantly: left ventricular from 12(1) to 20(2) mm Hg and right ventricular from 8(1) to 10(1) mm Hg. Right ventricular peak systolic pressure increased from 29(2) to 35(2) mm Hg while left ventricular peak systolic pressure did not change. One hour after infarction the half time of isovolumic relaxation of the right ventricle was prolonged from 6.9(0.5) to 8.7(0.4) ms. Ejection fraction in both ventricles was depressed: from 46(1) to 34(2)% in the right ventricle and from 69(3) to 49(3) in the left ventricle. There was no change in either right or left ventricular dP/dt. These data suggest that right ventricular systolic and diastolic dysfunction occurs as the result of an anteroseptal myocardial infarction in pigs.

Mexiletine in refractory ventricular arrhythmias.

The antiarrhythmic efficacy of mexiletine was evaluated in 28 subjects with recurrent ventricular tachycardia or fibrillation (22 subjects) or with symptomatic complex ventricular ectopy (six subjects). In all, either the arrhythmia was refractory to other drugs, or such therapy was not tolerated. Response to mexiletine was assessed by continuous ECGs, and in five cases by programmed electrical stimulation. Mexiletine abolished the arrhythmia in 12 cases, but was not tolerated long-term in four. Mexiletine was ineffective in 10 subjects. Seven subjects had significant adverse reactions during short-term dosing; in six, mexiletine was discontinued because of adverse effects after the first few doses so efficacy was not evaluated. The most common adverse effects were nausea, tremor, and generalized malaise. We conclude that mexiletine is an effective antiarrhythmic in some patients with life-threatening ventricular arrhythmias refractory to conventional drugs. Adverse effects significantly limit its use.

Continuous transtracheal oxygen delivery during cardiopulmonary resuscitation. An alternative method of ventilation in a canine model.

Adequate oxygenation of apneic subjects can be maintained by constant flow transtracheal oxygen (TTO), but this method alone is associated with hypercapnia. The "bellows" effect of external chest compressions (ECC) might prevent this problem if the airway were kept open by TTO. In dogs, we investigated the utility of TTO delivered at 15 L/min by a percutaneously placed intratracheal catheter, plus ECC (TTO/ECC) as an alternative method of ventilation during CPR. TTO was applied to anesthetized, paralyzed dogs in normal sinus rhythm (NSR) at various rates of ECC and during ventricular fibrillation (VF) at an ECC rate of 80/min. During NSR and VF, hypercapnia did not develop and arterial oxygen saturations were maintained above 90 percent. During NSR, the PaCO2 decreased and the pH increased as the ECC rate increased. For many of the animals, coronary perfusion pressure remained above 20 mm Hg during VF, suggesting that these animals could be resuscitated to NSR. In another phase, after 15 min of VF using TTO/ECC, seven of nine animals were defibrillated. We conclude that ventilatory and hemodynamic support adequate to permit successful resuscitation to NSR is provided by the combination of TTO/ECC to apneic dogs during VF.

Oxygenation and ventilation during cardiopulmonary resuscitation utilizing continuous oxygen delivery via a modified pharyngeal-tracheal lumened airway.

Use of continuous transtracheal oxygen delivery systems combined with rhythmic chest compressions can provide excellent oxygenation and ventilation during cardiopulmonary resuscitation. However, occasional displacement of the transtracheal catheter results in life-threatening pneumomediastinal complications. We investigated using the pharyngeal lumen of a pharyngeal-tracheal lumened airway (PtL) as an alternative delivery system for continuous oxygen flow in 21 large mongrel dogs. Excellent ventilation was possible in anesthetized, apneic, and paralyzed dogs in normal sinus rhythm from the "bellows" effect of chest compressions. The hypercapnia and respiratory acidemia resulting from 5 min of complete apnea in ten dogs during normal sinus rhythm was readily corrected (p less than 0.01). In an additional 11 dogs, external chest compressions were performed and oxygen was delivered continuously via the PtL during 20 min of ventricular fibrillation. During this period of cardiac arrest, pH declined (7.38 +/- 0.01 vs 7.19 +/- 0.02; p less than 0.01), but PaCO2 (35 +/- 1 vs 38 +/- 3 mm Hg) and PaO2 (67 +/- 2 vs 68 +/- 3 mm Hg) were not significantly different from prearrest values. Successful resuscitation was achieved in 8 of 11 (73 percent) animals, which is similar to the results in historical controls with endotracheal intubation. No pneumomediastinal complications were seen with use of the PtL. We conclude that using the pharyngeal lumen of the PtL for continuous delivery of oxygen combined with external chest compressions can provide a safe and effective mode of oxygenation and ventilation during cardiac arrest.

Evaluation of cardiomyoplasty and skeletal muscle ventricle procedures in a clinically realistic animal model.

Cardiomyoplasty and skeletal muscle ventricle procedures have shown increasing promise in the treatment of cardiomyopathy with associated chronic congestive heart failure. More than 100 patients have now received such procedures worldwide. The clinical results to date have been mostly anecdotal with subjective improvement but without firm objective data to collaborate the subjective impression. A clinically realistic animal model would have tremendous advantages to help elucidate the mechanisms by which cardiomyoplasty or skeletal muscle ventricles improve the sense of well-being of patients who have congestive heart failure. Several possible animal models exist, including pharmacologically induced congestive heart failure models and postischemic injury cardiomyopathy models. The most intriguing, however, is a spontaneously occurring cardiomyopathy in large dogs. This idiopathic cardiomyopathy that appears mainly in large-breed dogs (Great Danes, Dobermans, and Saint Bernards) has a rapidly progressive course; it has a 6-month mortality rate of 75% and a 12-month mortality rate of 95% to 100%. The most efficacious use of such an experimental model would include the evaluation of cardiomyoplasty and skeletal muscle ventricle procedures in a multidimensional fashion. Experimental endpoints should include mortality, exercise tolerance, systolic and diastolic ventricular function, and arrhythmia occurrence. Sophisticated techniques now exist for the evaluation of systolic and diastolic ventricular function. Such evaluation may well provide additional insight into how such experimental procedures benefit those with congestive heart failure.

Open-chest cardiac massage after closed-chest compression in a canine model: when to intervene.

Open-chest cardiac massage appears beneficial in improving hemodynamics during resuscitation efforts and in improving resuscitation success. The time between cardiac arrest and the initiation of open-chest cardiac massage is crucial. It would appear that if initiation of open chest cardiac massage is delayed for more than 20 min from the onset of cardiac arrest, little or no successful outcome can be expected. Further techniques for assessing the adequacy of closed-chest compression CPR are needed. Such techniques would allow early identification of ineffective resuscitation efforts and provide the opportunity for early change to other, presumably more effective, techniques.

Myocardial perfusion during cardiopulmonary resuscitation (CPR): effects of 10, 25 and 50% coronary stenoses.

Myocardial blood flow under normal physiologic conditions remains relatively unaltered by coronary lesions with diameter stenosis of less than 70%. However, during cardiac arrest and cardiopulmonary resuscitation (CPR), autoregulation of coronary blood flow is compromised. We studied the effect of previously considered 'trivial' coronary stenoses of 10, 25 and 50% on distal myocardial perfusion in 39 swine undergoing CPR for cardiac arrest. Endocardial blood flow distal to the stenosis was significantly less than that proximal in all the different stenoses groups (P < 0.05). A 50% diameter stenosis also compromised epicardial blood flow distal to the stenosis (P < 0.05). This study suggests that any coronary lesion may compromise myocardial perfusion during CPR. Since the vast majority of cardiac arrest victims have coronary artery disease, careful attention to maximizing myocardial blood flow during CPR is needed.