To shock or not to shock: that is the question.
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Electric Countershock↗
Biomedical subjects
R D White
Publications and source records attributed to R D White.
Technologic advances and program initiatives in public access defibrillation using automated external defibrillators.
Widespread provision of early defibrillation following cardiac arrest holds major promise for improved survival from ventricular fibrillation. The critical element in predicting a successful outcome is the rapidity with which defibrillation is achieved. A worldwide awareness of this potential and its advocacy by such organizations as the American Heart Association have been pivotal in the evolution of initiatives to make defibrillation more widely and more rapidly available. The feasibility of this initiative, known as public access defibrillation, is in large measure a direct consequence of major technologic advances in automated external defibrillators (AEDs). New low-energy waveforms with biphasic morphology have been shown to be more effective in terminating ventricular fibrillation and may do so with less myocardial injury. Placement of AEDs in a variety of nontraditional settings such as police cars, aircraft and airport terminals, and gambling casinos has been shown to yield an impressive number of survivors of cardiac arrest in ventricular fibrillation. Questions yet to be answered center on the appropriate disposition of AEDs in public access defibrillation settings, training and retraining issues, device maintenance, and collection of accurate data to document benefit and to identify areas of needed improvement or expansion of AED availability.
Automation↗
Viable myocardium in reperfused acute myocardial infarction: rest and stress first-pass mr imaging.
Feasibility of identifying viable myocardium in rest and stress magnetic resonance imaging (MRI) was evaluated using 3 hr occlusion and 30 min reperfusion model of left anterior descending (LAD) coronary artery in 12 felines. At rest MRI, viable myocardium confirmed by 2,3,5-triphenyl tetrazolium chloride (TTC)-staining showed rapid signal intensity (SI) rise followed by gradual decline not significantly different from normal myocardium that the two hyperperfused regions were distinguishable only from the hypoperfused nonviable myocardium. At stress MRI, hyperemia induced perfusion change was most pronounced in normal myocardium with earlier and greater peak enhancement followed by brisk 'washout' phase while minimally augmented enhancement in viable myocardium was still in 'washin' phase. From these findings, it was concluded that viable myocardium is identified in rest and stress MRI as redistributing hypo- perfusion compared to persistent hyper-perfusion of the normal myocardium and the persistent hypo-perfusion of the nonviable myocardium.
Animals↗
[Measurement of left atrial and ventricular volumes in real-time 3D echocardiography. Validation by nuclear magnetic resonance].
The measurement of the left ventricular ejection fraction is important for the evaluation of cardiomyopathy and depends on the measurement of left ventricular volumes. There are no existing conventional echocardiographic means of measuring the true left atrial and ventricular volumes without mathematical approximations. The aim of this study was to test anew real time 3-dimensional echocardiographic system of calculating left atrial and ventricular volumes in 40 patients after in vitro validation. The volumes of the left atrium and ventricle acquired from real time 3-D echocardiography in the apical view, were calculated in 7 sections parallel to the surface of the probe and compared with atrial (10 patients) and ventricular (30 patients) volumes calculated by nuclear magnetic resonance with the simpson method and with volumes of water in balloons placed in a cistern. Linear regression analysis showed an excellent correlation between the real volume of water in the balloons and volumes given in real time 3-dimensional echocardiography (y = 0.94x + 5.5, r = 0.99, p < 0.001, D = -10 +/- 4.5 ml). A good correlation was observed between real time 3-dimensional echocardiography and nuclear magnetic resonance for the measurement of left atrial and ventricular volumes (y = 0.95x - 10, r = 0.91, p < 0.001, D = -14.8 +/- 19.5 ml and y = 0.87x + 10, r = 0.98, P < 0.001, D = -8.3 +/- 18.7 ml, respectively. The authors conclude that real time three-dimensional echocardiography allows accurate measurement of left heart volumes underlying the clinical potential of this new 3-D method.
Aged↗
Get the data.
Numerous studies affirm the benefit of rapid defibrillation with AEDs. Most of the data have been acquired in emergency medical response systems with EMTs or firefighters providing defibrillation. Yet interest is growing in the provision of rapid defibrillation by other responders, including security officers, flight attendants and laypersons trained as targeted responders. This expansion is embraced in community early defibrillation. A multicenter, prospective, randomized, controlled trial was recently launched to define the benefit of community early defibrillation. Data from this trial will likely identify the most effective deployment of AEDs, frequency and appropriateness of use, time of defibrillation before EMS arrival, device maintenance issues and--most importantly--survival benefit when compared with control groups without AEDs.
Diffusion of Innovation↗
Heart-to-heart talk. Roundtable discussion.
This past August the American Heart Association (AHA) released a major revision of its recommendations for emergency cardiovascular care (ECC). The 2000 guidelines simplify CPR techniques for the layperson and strongly promote the use of community early defibrillation. What repercussions can we expect from these changes? We asked five experts to join a roundtable discussion of the BLS aspects of these new guidelines. Their conversation follows.
Cardiopulmonary Resuscitation↗
Validation of real-time three-dimensional echocardiography for quantifying left ventricular volumes in the presence of a left ventricular aneurysm: in vitro and in vivo studies.
OBJECTIVES: To validate the accuracy of real-time three-dimensional echocardiography (RT3DE) for quantifying aneurysmal left ventricular (LV) volumes. BACKGROUND: Conventional two-dimensional echocardiography (2DE) has limitations when applied for quantification of LV volumes in patients with LV aneurysms. METHODS: Seven aneurysmal balloons, 15 sheep (5 with chronic LV aneurysms and 10 without LV aneurysms) during 60 different hemodynamic conditions and 29 patients (13 with chronic LV aneurysms and 16 with normal LV) underwent RT3DE and 2DE. Electromagnetic flow meters and magnetic resonance imaging (MRI) served as reference standards in the animals and in the patients, respectively. Rotated apical six-plane method with multiplanar Simpson's rule and apical biplane Simpson's rule were used to determine LV volumes by RT3DE and 2DE, respectively. RESULTS: Both RT3DE and 2DE correlated well with actual volumes for aneurysmal balloons. However, a significantly smaller mean difference (MD) was found between RT3DE and actual volumes (-7 ml for RT3DE vs. 22 ml for 2DE, p = 0.0002). Excellent correlation and agreement between RT3DE and electromagnetic flow meters for LV stroke volumes for animals with aneurysms were observed, while 2DE showed lesser correlation and agreement (r = 0.97, MD = -1.0 ml vs. r = 0.76, MD = 4.4 ml). In patients with LV aneurysms, better correlation and agreement between RT3DE and MRI for LV volumes were obtained (r = 0.99, MD = -28 ml) than between 2DE and MRI (r = 0.91, MD = -49 ml). CONCLUSIONS: For geometrically asymmetric LVs associated with ventricular aneurysms, RT3DE can accurately quantify LV volumes.
Animals↗
In vitro metabolism of polychlorinated biphenyl congeners by beluga whale (Delphinapterus leucas) and pilot whale (Globicephala melas) and relationship to cytochrome P450 expression.
We measured rates of oxidative metabolism of two tetrachlorobiphenyl (TCB) congeners by hepatic microsomes of two marine mammal species, beluga whale and pilot whale, as related to content of selected cytochrome P450 (CYP) forms. Beluga liver microsomes oxidized 3,3',4,4'-TCB at rates averaging 21 and 5 pmol/min per mg for males and females, respectively, while pilot whale samples oxidized this congener at 0.3 pmol/min per mg or less. However, rates of 3,3',4,4'-TCB metabolism correlated with immunodetected CYP1A1 protein content in liver microsomes of both species. The CYP1A inhibitor alpha-naphthoflavone inhibited 3,3',4,4'-TCB metabolism by 40% in beluga, supporting a role for a cetacean CYP1A as a catalyst of this activity. Major metabolites of 3,3',4,4'-TCB generated by beluga liver microsomes were 4-OH-3,3',4',5-TCB and 5-OH-3,3',4,4'-TCB (98% of total), similar to metabolites formed by other species CYP1A1, and suggesting a 4,5-epoxide-TCB intermediate. Liver microsomes of both species metabolized 2,2',5,5'-TCB at rates of 0.2-1.5 pmol/min per mg. Both species also expressed microsomal proteins cross-reactive with antibodies raised against some mammalian CYP2Bs (rabbit; dog), but not others (rat; scup). Whether CYP2B homologues occur and function in cetaceans is uncertain. This study demonstrates that PCBs are metabolized to aqueous-soluble products by cetacean liver enzymes, and that in beluga, rates of metabolism of 3,3',4,4'-TCB are substantially greater than those of 2,2',5,5'-TCB. These directly measured rates generally support the view that PCB metabolism plays a role in shaping the distribution patterns of PCB residues found in cetacean tissue.
Animals↗
New digital measurement methods for left ventricular volume using real-time three-dimensional echocardiography: comparison with electromagnetic flow method and magnetic resonance imaging.
AIM: The aim of this study was to investigate the feasibility and accuracy of using symmetrically rotated apical long axis planes for the determination of left ventricular (LV) volumes with real-time three-dimensional echocardiography (3DE). METHODS AND RESULTS: Real-time 3DE was performed in six sheep during 24 haemodynamic conditions with electromagnetic flow measurements (EM), and in 29 patients with magnetic resonance imaging measurements (MRI). LV volumes were calculated by Simpson's rule with five 3DE methods (i.e. apical biplane, four-plane, six-plane, nine-plane (in which the angle between each long axis plane was 90 degrees, 45 degrees, 30 degrees or 20 degrees, respectively) and standard short axis views (SAX)). Real-time 3DE correlated well with EM for LV stroke volumes in animals (r=0.68-0.95) and with MRI for absolute volumes in patients (r-values=0.93-0.98). However, agreement between MRI and apical nine-plane, six-plane, and SAX methods in patients was better than those with apical four-plane and bi-plane methods (mean difference = -15, -18, -13, vs. -31 and -48 ml for end-diastolic volume, respectively, P<0.05). CONCLUSION: Apically rotated measurement methods of real-time 3DE correlated well with reference standards for calculating LV volumes. Balancing accuracy and required time for these LV volume measurements, the apical six-plane method is recommended for clinical use.
Adult↗
Persistent anterior maxillary bone loss.
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Adult↗
Potency preservation after three-dimensional conformal radiotherapy for prostate cancer: preliminary results.
We sought to assess potency preservation after three-dimensional conformal radiotherapy (3D-CRT) in prostate cancer patients eligible for radical prostatectomy, conventional radiotherapy, 3D-CRT, or transperineal prostate implantation. Patients with more advanced disease are commonly treated with hormonal therapy, which can cause impotence, and were consequently excluded from the analysis. Between December 1991 and June 1998, 198 prostate cancer patients were treated with 3D-CRT at the University of California, Davis Medical Center. Fifty-two of these patients had a pretreatment prostate-specific antigen (PSA) level of 10.0 ng/ml or less, a Gleason score of 6 or less, and a 1997 AJCC clinical stage T1bN0M0 to T2bN0M0. One patient was not evaluable. None of the 51 evaluable patients had diabetes mellitus. In 40 patients, the prostate gland only was irradiated to a total dose of 66 to 79.2 Gy by using daily 1.8-Gy fractions. In 11 patients, the prostate and seminal vesicles were treated to 44 to 55.8 Gy. Lymph nodes were not included in the clinical target volume. The median age was 68 years, and the median length of follow-up was 15 months. Potency in this study is defined as an erection sufficient for vaginal penetration. Kaplan-Meier analysis was used to describe potency as a function of time after 3D-CRT. Of the 51 evaluable patients, 35 (69%) were potent, 15 were impotent, and 1 was sexually inactive before 3D-CRT. Kaplan-Meier estimates of the potency preservation rates 1, 2, and 3 years after 3D-CRT are 100%, 83%, and 63%, respectively. On multivariate analysis, age, total radiation dose, and a history of transurethral resection of the prostate did not significantly affect potency preservation rates. Three (43%) of 7 patients who became impotent after 3D-CRT and used sildenafil were subsequently able to achieve erections sufficient for vaginal penetration. The preliminary results reported herein suggest that approximately two thirds of prostate cancer patients will retain their potency 3 years after 3D-CRT. Further follow-up is necessary to assess long-term potency after 3D-CRT. Sildenafil should be considered in patients who develop radiation-induced impotence.
3',5'-Cyclic-GMP Phosphodiesterases↗
Does intraoperative hetastarch administration increase blood loss and transfusion requirements after cardiac surgery?
UNLABELLED: Hetastarch is used for intravascular volume expansion in cardiac surgery. Studies show conflicting effects of intraoperative hetastarch administration on postoperative bleeding. Hetastarch was routinely used for volume expansion during cardiovascular surgeries at our institution until its use was discontinued intraoperatively. We performed a retrospective chart review on patients undergoing primary coronary artery bypass grafting, valve repair or replacement requiring cardiopulmonary bypass (n = 444), 234 of which received intraoperative hetastarch and 210 did not. There was no difference in demographics, cardiac surgery, or cardiopulmonary bypass duration between the two groups. Blood loss for 0-4 h postoperatively was 377 +/- 244 mL in the group not receiving hetastarch compared with 515 +/- 336 mL in the group that received hetastarch (P < 0.001). For 0-24 h postoperatively, blood loss was 923 +/- 473 mL versus 1,283 +/- 686 mL in the absence and presence of hetastarch, respectively (P < 0.001). Allogeneic transfusion requirements (cryoprecipitate, fresh frozen plasma, and platelets) were larger in the hetastarch group (all P < 0.001). Nearly all (99%) patients in the hetastarch group received less than the manufacturer's recommended dose (20 mL/kg) of hetastarch. IMPLICATIONS: Our large retrospective study suggests that intraoperative use of hetastarch in primary cardiac surgery with cardiopulmonary bypass may increase bleeding and transfusion requirements. A large prospective study is needed to determine if intraoperative administration of hetastarch should be avoided during cardiovascular surgery.
Aged↗
Imaging of cardiac and paracardiac masses.
Magnetic resonance imaging (MRI) and computed tomography (CT) are important imaging modalities for the noninvasive characterization of cardiac and paracardiac masses. They are, in general, superior to other modalities (e.g., echocardiography) in their ability to delineate the exact location and the extent of the lesion and to demonstrate the effects of the lesion on surrounding structures. MRI and CT may also be helpful in suggesting a specific diagnosis, because some tumors have rather characteristic locations and appearances. In addition, both modalities can be extremely helpful in both treatment planning and posttreatment follow-up because they are noninvasive, reproducible, and enable detection of residual or recurrent mass.
Heart Neoplasms↗
Estimation of current leakage in left and right ventricular conductance volumetry using a dynamic finite element model.
Leakage of electric current through cardiac structures surrounding the ventricle is a primary source of error during ventricular volume measurements using a conductance catheter. This error can be represented as a leakage volume, VL. VL is generally estimated by a saline-bolus method, and is assumed constant throughout the cardiac cycle. However, dynamic changes in ventricular volume and cardiac wall thickness could change VL. To estimate VL, a dynamic finite element model of the heart was developed based on MR images. Conductance measurements were simulated using a modeled conductance catheter, and true VL was calculated. VL varied from 22.7 ml (end-systole) to 26.4 ml (end-diastole) in the left ventricle and from 19.9 ml (end-systole) to 26.9 ml (end-diastole) in the right ventricle. The saline-bolus method underestimated VL in both the left (VL = 19.4 ml) and the right (VL = 4.1 ml) ventricular volume measurements. VL increased linearly with the ratio of blood to tissue resistivity, and changed minimally with catheter position. These results indicate that VL has to be estimated dynamically throughout the cardiac cycle to obtain accurate cardiac volume measurements. The results also show that the saline bolus method does not estimate current leakage accurately, especially in the right ventricular volume measurement.
Biomedical Engineering↗
20 of the most influential people in EMS. Part 2. Interview by Mike Taigman.
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Emergency Medical Services↗
Initial clinical experience of real-time three-dimensional echocardiography in patients with ischemic and idiopathic dilated cardiomyopathy.
The geometry of the left ventricle in patients with cardiomyopathy is often sub-optimal for 2-dimensional ultrasound when assessing left ventricular (LV) function and localized abnormalities such as a ventricular aneurysm. The aim of this study was to report the initial experience of real-time 3-D echocardiography for evaluating patients with cardiomyopathy. A total of 34 patients were evaluated with the real-time 3D method in the operating room (n = 15) and in the echocardiographic laboratory (n = 19). Thirteen of 28 patients with cardiomyopathy and 6 other subjects with normal LV function were evaluated by both real-time 3-D echocardiography and magnetic resonance imaging (MRI) for obtaining LV volumes and ejection fractions for comparison. There were close relations and agreements for LV volumes (r = 0.98, p <0.0001, mean difference = -15 +/- 81 ml) and ejection fractions (r = 0.97, p <0.0001, mean difference = 0.001 +/- 0.04) between the real-time 3D method and MRI when 3 cardiomyopathy cases with marked LV dilatation (LV end-diastolic volume >450 ml by MRI) were excluded. In these 3 patients, 3D echocardiography significantly underestimated the LV volumes due to difficulties with imaging the entire LV in a 60 degrees x 60 degrees pyramidal volume. The new real-time 3D echocardiography is feasible in patients with cardiomyopathy and may provide a faster and lower cost alternative to MRI for evaluating cardiac function in patients.
Cardiac Volume↗
Improving survival following out-of-hospital cardiac arrest.
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Electric Countershock↗
Role of transesophageal echocardiography in assessing diastolic dysfunction in a large clinical practice: a 9-year experience.
BACKGROUND: Two-dimensional transthoracic echocardiography with respiratory monitoring has been used to characterize diseases that impair diastolic function. Transesophageal echocardiography (TEE) has emerged as a complementary technique to evaluate patients with these diseases. The purpose of this study was to evaluate in a large clinical practice the utility of TEE with respiratory monitoring for classification of patients with diastolic dysfunction. METHODS: Over a 9-year period TEE was used to examine 192 patients referred to an echocardiography laboratory for additional evaluation of abnormal diastolic function. We performed pulsed-wave Doppler TEE of the left ventricular inflow and pulmonary veins and respiratory monitoring to categorize patients as showing restrictive physiologic features, constriction with or without effusion, mixed constriction and restriction, abnormal relaxation, pseudonormalization, large pericardial effusion or tamponade, or normal diastolic function. RESULTS: Patients with diastolic dysfunction underwent 3% of the total number of transesophageal studies conducted during the study period. Among the 192 patients referred for TEE, abnormal diastolic function was found in 181 (94%); 11 (6%) had normal diastolic function. Seventy-one (39%) of the 181 patients had restrictive physiologic features. Constrictive pericarditis was found in 54 (30%) of the patients and was confirmed for all 31 patients who underwent pericardiectomy. Mixed constriction and restriction was present in 21 (12%) of the patients. The other 35 patients (19%) had abnormal relaxation, pseudonormalization, or large pericardial effusion or tamponade. The cause of diastolic dysfunction was idiopathic for 32% of the patients, previous cardiac operation for 26%, cardiac amyloidosis for 23%, radiation therapy for 11%, and hypertension or advanced ischemic heart disease for 8%. CONCLUSION: Two-dimensional and Doppler TEE with respiratory monitoring is useful in categorizing patients with impaired diastolic function, primarily into those with restrictive physiologic features or constrictive pericarditis.
Adult↗