[Renal sympathetic denervation--physical-antomical basics, procedure, and analysis of clinical and technical parameters on procedure success and efficacy]. / Renale sympathische Denervierung: physikalisch-anatomische Grundlagen, technisches Vorgehen und Analyse klinischer und technischer Einflussgrößen auf die Effizienz der Hochfrequenzablation.

BACKGROUND: Evidence from human and animal models indicate that excessive central sympathetic nerve activity (SNA) plays a pathogenic role in triggering and sustaining hypertension. Thus, treatments targeting this neurogenic (sympathetic) triggered hypertension were evaluated and renal sympathetic denervation (RND) showed promising results. However, little is known about the parameters influencing efficacy of high frequency energy in the arterial model. PATIENTS AND METHODS: Data from all 40 consecutive patients suffering from therapy-resistant hypertension who underwent RND and completed a 1-year follow-up were retrospectively analyzed. We focussed on procedural success, complications and efficacy (office-blood pressure, 24-h-blood pressure) and its correlations to quantity of ablations and intima media thickness. RESULTS: In all patients (65.9 ± 11.6 years (range 42-83); 72.5% male) the procedure was successful. Ablations with arterial access from the upper extremity were technically unsuccessful. With the use of 13.6 ± 1.7 (10-17) ablations, office-blood pressure (1-year) could be reduced from 162/89 mmHg to 142/82 mmHg and 24-h-blood pressure from 149/83 mmHg to 139/79 mmHg, respectively, including a medium to strong correlation to quantity of ablations (r = 0.57, r = 0.63) while documenting only a weak correlation to IMT (r = -0.29, r = -0.25). CONCLUSION: In comparison to the Simplicity studies, the hypertension lowering effects were less profound but consistently present over time in the 24-h-blood pressure assessments. The positive correlation of the quantity of ablations we found seems to be plausible regarding the unpredictable allocations of the sympathetic nerves i.e. in profoundly kinking vessels in hypertensives. The physics of high-frequency energy application in the arterial model needs further research.

The concept of an anatomy related individual arterial access: lowering technical and clinical complications with transradial access in bovine- and type-III aortic arch carotid artery stenting.

BACKGROUND: Carotid artery stenting (CAS) from the femoral approach can be anatomically very difficult and the incidence of complications is higher in patients with anatomical variations of the aortic arch, difficulties related to peripheral vascular disease and/or with access site complications. Because the typical morphology in patients with a bovine- or type-III aortic arch applies for an arterial access from the right upper extremity (e.g. radial, brachial) we evaluated success rates and safety of the right transradial access in a prospective study. PATIENTS AND METHODS: Between June 2009 and October 2010, seventeen patients (mean age 74,4 ± 9 years, 10 male) with a bovine- (n = 4) or type-III aortic arch (n = 12) underwent CAS with a planned transradial- (n = 3) or after problematic transfemoral access (n = 14). In patients with a type-III aortic arch (n = 13), the right target common carotid artery (CCA) was cannulated from the right radial artery with a 5F IMA diagnostic catheter-, in patients with a bovine aortic arch (n = 4), the left CCA was accessed from the right radial artery with a 5F Amplatz- or Judkins left catheter. In all patients a 6F- (n = 14) or 5F- (n = 3) shuttle sheath was inserted via the diagnostic catheter and a 0.035” extra-stiff guidewire. All interventions were carried out with the use of a peripheral embolization protection device (EPD). Primary study endpoints were procedural success and major adverse cardiac and cerebrovascular events (MACCE), secondary endpoints were access site complications and the mean intervention time. RESULTS: Procedural success could be achieved in all patients (100 %), MACCE and access site complications did not occur in any patient. Mean interventional time was 48 ± 18 min. CONCLUSIONS: CAS using the right transradial approach for left CAS in bovine-type aortic arch or the right transradial approach in type-III aortic arch for right CAS appears to be safe and technically feasible.

Transradial access in percutaneous coronary interventions: technique and procedure.

After showing significantly lower complication rates in diagnostic coronary angiography, the radial artery access was successfully introduced as a useful vascular access site for transradial percutaneous coronary intervention in order to enhance patients' comfort and reduce hospital workload and costs. Moreover, due to the reduced need for antiplatelet therapy cessation as a result of lower bleeding complications, patients treated with transradial access showed a significantly better cardiac outcome in randomized interventional acute coronary syndrome studies.Procedural success and postprocedural radial arteritis or radial occlusions are closely related to anatomical circumstances (e.g., anomalous radial branching patterns, tortuosity, e.g., radial loops and small radial artery diameters), or risk factors for radial spasms (e.g. smoking, anxiety, vessel diameter, age, gender) which can effectively be reduced by the use of smaller catheters (4-5 Fr) and the administration of an adjuvant pharmacological therapy before (3000 U heparin, verapamil, nitroglycerine) and after (ibuprofen) the intervention.For successful radial sheath access and transradial catheterization, it is important to use dedicated radial access needles ≤ 21-gauge and steel wires ≤ 0.018 in. In order to pass the brachiocephalic trunk without difficulties or complications and access the ascending aorta, the use of inspiration maneuvers is of central importance.

[1-(11)C]Acetate as a quantitative perfusion tracer in myocardial PET.

UNLABELLED: Our objective was to investigate the properties of [1-(11)C]acetate as a quantitative perfusion tracer for myocardial PET studies. METHODS: We determined the flow dependence of the effective acetate extraction by a comparison with [(13)N]ammonia in 24 patients at rest (n = 8) and under pharmacologic vasodilation (n = 16). Furthermore, we compared the statistical quality of the perfusion values derived with both tracers. Quantification was based on an irreversible 2-compartment model for [(13)N]ammonia and a reversible 1-compartment model for [1-(11)C]acetate. Area-conserving polar maps were used to determine the correlation between the unidirectional uptake parameters of both tracers on a pixel-by-pixel basis for the whole left ventricular myocardium. RESULTS: A fit of a generalized Renkin-Crone formula to the data yielded the unidirectional acetate extraction fraction E(f) = 1 - 0.64e(-1.20/f). An extraction correction based on this formula led to good quantitative agreement of perfusion values derived with [(13)N]ammonia and [1-(11)C]acetate over the whole observed flow range (average difference of flow values, 3%; correlation coefficient, 0.96). This agreement proved the applicability of acetate as a quantitative perfusion tracer even under stress conditions. An analysis of the statistical properties of the parameter estimates showed, moreover, that statistical errors were reduced by a factor of nearly 2 in comparison with ammonia. CONCLUSION: [1-(11)C]acetate allows accurate quantification of myocardial perfusion with PET at rest as well as under stress conditions. The use of acetate leads to distinctly improved statistical accuracy for the perfusion estimates in comparison with ammonia. This accuracy facilitates the generation of reliable parametric polar maps, which are especially useful for clinical application of myocardial perfusion quantification.

Incomplete expansion of Palmaz-Schatz stents despite high-pressure implantation technique: impact on target lesion revascularization.

Improved expansion of stents using high-pressure implantation technique with subsequent antiplatelet therapy has improved patient outcome regarding the incidence of subacute stent thrombosis, bleeding complications and restenosis. Whether high-pressure implantation per se guarantees adequate stent expansion remains unclear. The aim of the study was to determine (1) stent expansion after high-pressure implantation technique and (2) whether stent expansion influences rate of target lesion revascularization within 6 months of follow-up. One hundred Palmaz-Schatz stents were implanted in 98 lesions (91 native vessels, 7 graft vessels) of 94 patients using high-pressure implantation technique (balloon pressure 12-20 atm). Stent expansion was investigated using intravascular ultrasound imaging (IVUS). Clinical follow-up of the patients was performed for 6 months. After implantation, stent/mean reference ratio was 0.81 +/- 0.16. Noncompliant balloons used for implantation were chosen by angiographic criteria. Mean balloon/reference ratio was 1.08 +/- 0.22; therefore balloons were not undersized. Additional balloon dilataion using higher pressures and/or larger balloons based on IVUS criteria and subsequent IVUS measurements was performed in 52 patients (55%); in these patients, stent expansion improved from 79 +/- 16 to 91 +/- 15% (mean +/- SD) of average reference areas (p < 0.002). Within the 6 months' clinical follow-up, target lesion revascularization was performed in 19 patients (20%). The only prognostic factors for the development of in-stent restenosis requiring target lesion revascularization were the vessel size (p < 0.05) and the extent of plaque distal to the stents (p < 0.05). Implantation of Palmaz-Schatz stents using high-pressure technique does not guarantee adequate stent expansion. Additional dilatation with higher pressures and/or larger balloons improves stent expansion. The size of the stented vessel and the extent of plaque at the distal stent end (residual outflow stenosis) but not the degree of stent expansion were predictors for target lesion revascularization within 6 months' follow-up.

Intravascular ultrasound and stent implantation: intraobserver and interobserver variability.

BACKGROUND: Intravascular ultrasound (IVUS) imaging can be used to optimize implantation of intracoronary stents; the variability of the measurements, however, remains unclear. Our aim in this study was to determine the intraobserver and interobserver variability of IVUS measurements after stent implantation. METHODS: Ninety-four patients underwent implantation of 100 Palmaz-Schatz stents in 98 lesions (79 de novo and 19 restenotic). IVUS measurements (3.5F, 30 MHz) of proximal and distal reference sections and of the smallest stent lumen were performed by 2 investigators. RESULTS: Intraobserver and interobserver correlations, respectively, were r = 0.96 and 0.93 for the proximal reference, r = 0.94 and 0.92 for the distal reference, and r = 0.97 and 0.97 for minimal stent lumen. Stent expansion (minimal lumen in the stent/mean reference area) showed a variability of r = 0.80 and 0.70. Taking a cutoff point of 90% for adequacy of stent expansion, observers agreed in only 77% whether the stent was adequately or inadequately expanded. CONCLUSIONS: IVUS enables reproducible lumen measurements in stents and reference sections. The degree of stent expansion, however, underlies a high measurement variability that can lead to different therapeutic strategies.

Angiographically undetected plaque in the left main coronary artery. Findings of intravascular ultrasound imaging.

The absence of angiographic findings despite significant coronary artery disease has been previously described. Possible explanations for the limitation of plaque detection by angiography include compensatory vessel enlargement in face of intracoronary plaque formation, the lack of reference segments in diffuse atherosclerosis as well as technical limitations. Intracoronary ultrasound (ICUS) imaging provides the possibility of direct plaque visualization. We studied angiographically normal left main coronary arteries (LMCA) in 72 patients prior to diagnostic angiography or therapeutic interventions using ICUS (30 MHz). ICUS images were continuously recorded and recalled from memory for morphometric analysis. Lumen area, plaque area and the total vessel area were determined by computer software. ICUS imaging revealed atherosclerotic plaque in 55 of the 72 patients with angiographically normal LMCA (76%). The average plaque area stenosis was 22 +/- 12% (range 3-44%). Total vessel area showed a significant direct correlation with plaque area, indicating compensation of coronary plaque formation. The average percent change in plaque area (difference between maximal and minimal plaque area within the LMCA) was 11 +/- 19%, indicating a diffuse pattern. Measurement of change in lumen area (difference between maximal and minimal lumen area within the LMCA) revealed an average value of 6 +/- 7%. Lumen area of the LMCA was 15.9 +/- 3.2 mm2 in patients with and 17.2 +/- 1.9 mm2 without atherosclerotic plaque (n.s.). Thus, the lack of angiographic changes despite advanced plaque formation in the LMCA could be explained by compensatory vessel enlargement and by diffuse distribution of plaque in the vessel; true lumen narrowings overlooked by angiography seem not to account for the failure of angiography to detect plaque.

Assessment of myocardial viability by use of 11C-acetate and positron emission tomography. Threshold criteria of reversible dysfunction.

BACKGROUND: Dual positron emission tomography (PET) imaging with a perfusion tracer and 18F-fluorodeoxyglucose (FDG) can detect myocardial viability. This approach may be replaced by a single 11C-acetate study, which enables quantification of both regional blood flow and oxidative metabolism. The significance of acetate-derived indexes for myocardial viability is examined. METHODS AND RESULTS: Thirty postinfarct patients with akinetic ventricular segments, a mean ejection fraction of 42 +/- 11%, and high-grade coronary obstructions were studied with serial 11C-acetate PET scanning before and 7 +/- 5 months after coronary revascularization. Acetate PET was tested against FDG and serial assessments of segmental wall motion. Sixty of 155 severely dysfunctional LV segments improved postoperatively, and regional blood flow increased. Flow estimates after revascularization suggested little fibrosis in reversible segments. At baseline, blood flows differed between normal myocardium, reversible dysfunction, and irreversible dysfunction (1.04 +/- 0.27, 0.73 +/- 0.18, and 0.43 +/- 0.18 mL.min-1.g-1, respectively; P < .001). Oxidative metabolic rates were reduced only in irreversibly injured LV segments. Multivariate analysis identified the acetate perfusion index as the only independent predictor of postoperative recovery. Its predictive accuracy was similar to that of FDG imaging but superior to indexes of flow-metabolic mismatch or oxidative metabolism. CONCLUSIONS: After myocardial infarction, quantitative indexes of perfusion and oxidative metabolism from acetate PET indicate a critical threshold beyond which tissue is irreversibly injured. Findings support the use of blood flow as a marker of myocardial viability in chronic postinfarct patients with modestly reduced ejection fractions.

Posttraumatic myocardial infarction with severe coronary intimal dissection documented by intravascular ultrasound.

We present a case of posttraumatic myocardial infarction after blunt chest trauma in a previously healthy man. Coronary angiography showed an eccentric occlusion in the midportion of the left anterior descending artery. Subsequent intracoronary ultrasound imaging revealed a severe intimal dissection. The outcome after intracoronary stent placement was excellent. This rare but potentially harmful complication of blunt chest trauma should be kept in mind and coronary angiography performed immediately when coronary occlusion is suspected. Intravascular ultrasound imaging is a helpful tool in the assessment of coronary artery occlusion caused by intimal dissection.

A kinetic model for cardiac PET with [1-carbon-11]-acetate.

UNLABELLED: Carbon-11-labeled acetate is a unique tracer for noninvasive assessment of myocardial oxidative metabolism with PET. Because adequate kinetic models have been missing, data evaluation in the past was performed mostly with phenomenological approaches such as mono- or biexponential fitting which cannot account for the influence of finite input duration and blood volume encountered in noninvasive PET investigations. METHODS: To investigate to what extent the current data evaluation schemes are justified, we developed a comprehensive model of [1-11C]-acetate kinetics in the myocardium which incorporates five tissue compartments: free acetate, activated acetate, CO2 precursors, amino acids and CO2. We derived the analytical solution of the model equations which is used for simulations and data fitting. RESULTS: The five-compartment model can reproduce in detail known experimental data. The resulting values of the eight model parameters compare favorably with existing biochemical facts. We have established the relation between parameters of the detailed model and one- and two-compartment models used for the evaluation of PET investigations. CONCLUSION: The kinetics of [1-11C]-acetate are adequately described by a five-compartment model. One- and two-compartment models are sufficient for simultaneous quantitative assessment of myocardial oxidative metabolism and perfusion with [1-11C]-acetate and PET.

[Coronary reserve after orthotopic heart transplantation: quantification with N-13 ammonia and positron emission tomography]. / Koronarreserve nach orthotoper Herztransplantation: Quantifizierung mit N-13-Ammoniak und der Positronenemissionstomographie.

Coronary transplant vasculopathy is known to be associated with an early impairment of endothelium-dependent vasodilatation. In this study the largely endothelium-independent dilator response to dipyridamole was evaluated in 22 patients 36 +/- 17 months after transplantation in relation to their angiographic findings. The dipyridamole coronary reserve was measured by N-13 ammonia and positron emission tomography (PET). Transplant vasculopathy was suspected or evident in 13 of 22 patients by coronary angiography. Coronary reserve was lower in transplant recipients than in normal controls (2.3 +/- 0.9 vs. 4.7 +/- 1.4). Those with a normal angiogram had a near normal minimal coronary resistance (0.3 +/- 0.04 mmHg.min.100 g/ml) and a normalized coronary reserve after correction for the increased resting blood flow (4.8 +/- 0.7). However, in patients with angiographic vasculopathy, coronary reserve was markedly reduced (1.8 +/- 0.7, corrected 2.7 +/- 1.0) and minimal coronary resistance was elevated (0.6 +/- 0.3, p < 0.001). Moreover, regional coronary reserve was homogeneously reduced throughout the myocardium without a clear segmental relationship to angiographic stenoses. After testing of other factors known to influence coronary resistance, our data are compatible with diffuse obstructions of the microvascular bed that are associated with an angiographically visible vasculopathy. The evaluation of coronary reserve by dipyridamole and PET provides a useful extension of angiography in these patients.

An approach to ventricular efficiency by use of carbon 11-labeled acetate and positron emission tomography.

BACKGROUND: Positron emission tomography-derived 11C-labeled acetate kinetics have been shown to reflect myocardial oxidative metabolism. The objective of the study was to use this metabolic imaging technique in combination with an evaluation of left ventricular work as an index of ventricular mechanical efficiency. METHODS AND RESULTS: The effects of ventricular ejection fraction and loading on this index were studied quantitatively in a canine experimental model. There was a curvilinear relationship between efficiency and the end-diastolic volume per unit mass (r = 0.84), which appeared to integrate the main determinants of left ventricular mechanical performance successfully and allowed the detection of a decreased ventricular efficiency in acute experimental heart failure. CONCLUSIONS: This approach appears to have the potential to assess the energetic working point of the ventricle in clinical heart disease and follow the effects of therapy. The data demonstrate the feasibility of an estimate of ventricular efficiency that relies on noninvasive data-acquisition techniques.

The effects of afterload reduction on myocardial carbon 11-labeled acetate kinetics and noninvasively estimated mechanical efficiency in patients with dilated cardiomyopathy.

METHODS AND RESULTS: With echocardiography and dynamic carbon 11-labeled acetate (C-11 acetate) positron emission tomographic imaging, C-11 acetate kinetics and a parameter that estimates mechanical ventricular efficiency (the work metabolic index) were defined in eight patients with dilated cardiomyopathy. The effect of afterload reduction with nitroprusside on these parameters was evaluated in six of these patients. Nitroprusside increased stroke work index but decreased the C-11 clearance rate. The work metabolic index determined noninvasively increased and correlated well with an invasive approach. The work metabolic index was inversely correlated with systemic vascular resistance. Nitroprusside shifted this relationship upward and to the left. CONCLUSION: This method of estimating efficiency is feasible and may represent a unique noninvasive approach for the evaluation of cardiac performance and responses to therapy.

Effect of carbon-11-acetate recirculation on estimates of myocardial oxygen consumption by PET.

Mono- and biexponential fitting of myocardial 11C-acetate kinetics does not account for the effect of recirculating 11C activity following intravenous injection of the tracer. A tracer kinetic model comprising two and three compartments was developed to describe intravascular and myocardial 11C-acetate kinetics defined by PET. This model approach including a correction for 11C-metabolites in blood was validated by correlating the model parameter estimates with directly measured oxygen consumption (MVO2) in 11 closed-chest dog experiments over a wide range of cardiac work. The model parameter k2 closely correlated with oxygen consumption (r = 0.94). This approach was subsequently applied to human studies and k2-related to rate-pressure product (PRP). In comparison to conventional monoexponential fitting of 11C-acetate tissue kinetics, the model approach improved the correlation coefficients of scintigraphic MVO2 estimates and PRP values from 0.61 to 0.91. Thus, analysis of myocardial 11C-acetate and clearance kinetics with a tracer kinetic model corrects for recirculating 11C-activity and may provide more consistent estimates of myocardial oxygen consumption.

Transport of inert gases in mammalian myocardium: comparison with a convection-diffusion model.

Because tracer techniques are gaining an increasing importance for imaging flow (and metabolism) in the heart, experimental evidence is needed on the role of convection and diffusion in the transcoronary transport of solutes. In the present work, the transport of four different inert gases through the coronary system is studied in five closed-chest dog experiments and is compared with a digital multicapillary convection-diffusion model. Transport may be defined as flow dependent, as judged by the gross similarity of shape of the time-normalized dilution curves. However, the results show that the transcoronary transport of helium and xenon is more dispersed than that of argon and krypton, probably because of differences in diffusibility and solubility. A comparison of the animal and model experiments emphasizes the importance of diffusive transport of the gases. It is suggested that there is a diffusion shunt that is mainly located within the capillary network itself rather than between conduit vessels. Only for helium (which has the highest diffusivity) was a small arteriovenous shunt fraction seen that is thought to bypass the capillary exchange region. The conclusion is that although there is evidence of diffusional shunting at a capillary level, the inert gas kinetics in the heart are compatible with a basically flow-limited transport.

Heterogeneity of myocardial blood flow under normal conditions and its dependence on arterial PO2.

We studied the heterogeneity of myocardial blood flow in nine anesthetized closed-chest dogs using an indicator-dilution technique that allows the stochastic description of transport characteristics for three inert gases (helium, argon, and xenon) from the coronary inflow to outflow. The results show that under normal conditions the transcoronary transport of the tracers is spatially heterogeneous. Heterogeneity is strongly dependent on the arterial oxygen tension over a range of 40-200 Torr. This could be similarly observed with each tracer gas despite different physicochemical properties and was largely independent from the magnitude of coronary blood flow. The results are interpreted to mean that the arteriolar or intratissue PO2 influences myocardial blood flow over a broad range and possibly acts as an important integrating factor in the local regulation of coronary blood flow and flow reserve.

Comparison of the effects of right atrial, right ventricular apex and atrioventricular sequential pacing on myocardial oxygen consumption and cardiac efficiency: a laboratory investigation.

As the impact of cardiac pacing on myocardial energetics has not yet been established, this laboratory investigation was undertaken to evaluate the effects of right atrial (AP), right ventricular apex (VP) and atrioventricular sequential pacing (AVP) on cardiac energetics in a closed-chest model. Ninety-two pacing interventions were performed in ten anesthetized mongrel dogs with normal loading conditions and contractile states. The energetic effects of pacing were assessed in terms of myocardial oxygen consumption (MVO2), its hemodynamic determinants and cardiac efficiency. Efficiency was calculated as the ratio of O2-equivalent of external cardiac work to MVO2, using standard definitions. In the first series of experiments 36 intra-individual comparisons were made between AP and VP at identical rates (95-210 beats/min). In the second series AVP was compared to VP in 10 intra-individual comparisons at identical rates (109-190 beats/min). MVO2 was lower (p less than 0.001) during AP (8.30 +/- 2.14 ml O2/min.100 g) compared to VP (10.16 +/- 3.15 ml O2/min.100 g) at the same rate (158 +/- 32 beats/min). Efficiency (p less than 0.001) was considerably higher during AP (21.6 +/- 5.7%) compared to VP (12.8 +/- 5.9%). During AVP, MVO2 (10.85 +/- 1.76 ml O2/min.100 g) was not significantly different from VP (10.57 +/- 1.34 ml O2/min.100 g) at the same rate (146 +/- 25 beats/min). Hemodynamics were superior with AVP compared to VP. Efficiency was significantly higher (p less than 0.01) with sequential (15.4 +/- 3.9%) as compared to ventricular pacing (12.0 +/- 3.2%). In conclusion, this study indicated that VP exerts disadvantageous effects on MVO2 and cardiac efficiency. AP has beneficial effects on cardiac energetics because it improves the relationship between mechanical performance of the heart and its energy requirements. AVP results in a higher efficiency than VP due to superior hemodynamics, despite MVO2 levels comparable to those of VP. The mechanism of energy waste with right ventricular apex pacing is probably related to an asynchronous contraction in the ventricular myocardium due to a nonphysiological spread of excitation.

Thermal recovery after passage of the pulmonary circulation assessed by deconvolution.

For indicator-dilution studies, complete thermal recovery after passage of heat through the pulmonary circulation would be desirable. However, the results in the literature obtained by extrapolation techniques are inconsistent. To overcome problems of the extrapolation approach, transport functions of the pulmonary circulation (including the left heart) were computed by deconvolution of pulmonary arterial and aortic pairs of thermodilution curves after central venous indicator injection (10 ml of an ice-cold blood indocyanine green dye mixture). Thermal recovery was determined as the finite integral of the transport function. Thirteen mongrel dogs under piritramid-N2O anesthesia were examined under base-line conditions, in orthostasis to alter the distribution of pulmonary blood flow (9 dogs), and in oleic acid edema (8 dogs). Using the deconvolution approach, thermal recovery was 0.97 +/- 0.04 under base-line conditions, 0.96 +/- 0.03 in orthostasis, and 0.96 +/- 0.05 in pulmonary edema. Thermal recovery determined from extrapolated dilution curves was greater than 100% in all groups, a physically impossible finding. It is concluded that thermal recovery is incomplete but insensitive with respect to the distribution of blood flow and to the size of the extravascular compartment. Monoexponential extrapolation is unsuited for the determination of thermal recovery.

Evaluation of monoexponential extrapolation of transpulmonary thermal-dye kinetics by use of a new model-free deconvolution algorithm.

This study evaluates the routine mathematic approach (monoexponential extrapolation) for analysis of transpulmonary thermal-dye dilution curves and estimates the effects of systemic-indicator recirculation by use of a deconvolution technique. Fifteen dogs anesthetized with N2O-piritramid were studied before and after induction of pulmonary edema by oleic acid. After introduction of central venous indicator (10 ml of a mixture of cold blood and indocyanine green dye), dilution data were recorded from the pulmonary artery and the ascending aorta. The conclusions were: (1) monoexponential extrapolation yields reasonably good estimates of the mean transit times of dye; (2) mean transit times of heat are usually overestimated by monoexponential extrapolation; (3) extravascular lung thermal volume assessed by monoexponential extrapolation is overestimated by 2.03 ml/kg of body mass under baseline conditions; and (4) the prepulmonary volume of distribution of heat exceeds that of dye by 1.4 ml/kg of body mass, thus increasing the overestimation of pulmonary extravascular heat-accessible space by the conventional technique.