P3589New generation stents for primary percutaneous coronary intervention in patients with acute myocardial infarction: evidence from an individual patient data network meta-analysis of randomized clinical

Background

Drug-eluting stents have shown their superiority in primary percutaneous intervention in patients with ST-segment elevation myocardial infarction (STEMI). No specific stent type has fully proven its superiority over others.

Purpose

We sought to compare the safety and efficacy of coronary artery stents in STEMI patients undergoing primary PCI through comprehensive network meta-analysis (NMA).

Methods

We performed an individual patient data (IPD) NMA of dedicated randomized trials in STEMI patients treated with coronary stents. The primary endpoint of interest was the composite outcome of cardiac death, any myocardial infarction (MI) or target lesion revascularization (TLR). Secondary outcomes were the individual component of the primary endpoint and definite or probable stent thrombosis. Outcomes were analyzed at the longest available follow-up. The primary analysis was performed using a one-stage random-effects meta-analysis.

Results

IPD from 15 randomized trials in STEMI patients were obtained including a total of 10,979 patients. Six different stent types were studied including bare metal stents (BMS), durable-polymer paclitaxel-eluting stents (DP-PES), durable-polymer sirolimus-eluting stents (DP-SES), durable-polymer zotarolimus-eluting stents (DP-ZES), durable-polymer everolimus-eluting stents (DP-EES) and biodegradable-polymer biolimus-eluting stent (BP-BES).

Mean patient age was 60.7±11.9 years; 22.7% were female and 16.1% were diabetic. Median symptom onset to balloon time was 210 min.

At a median follow-up of 3 years (interquartile range 2–4.9 years), patients treated with second-generation (DP-EES and BP-BES) or first-generation DES (DP-PES, DP-SES and DP-ZES) had significantly lower risk of the primary endpoint than patients treated with BMS (BMS vs. second-generation DES; HR 0.69, 95% CI 0.57–0.82, BMS vs. first-generation DES; HR 0.70, 95% CI 0.61–0.80). The differences were driven by the significant reduction of TLR associated with first- and second-generation DES compared with BMS. A trend towards lower risk of MI with second-generation DES compared with BMS or first-generation DES was observed (BMS vs. second-generation DES; HR 0.79, 95% CI 0.58–1.06, first- vs. second-generation DES; HR 0.75, 95% CI 0.54–1.03). Second-generation DES was associated with a significantly lower risk of definite or probable stent thrombosis compared with BMS (HR 0.62, 95% 0.40–0.97) and first-generation DES (HR 0.55, 95% CI 0.34–0.91). DP-EES and BP-BES had a similar risk of the primary endpoint, individual components of the primary endpoint, and definite or probable stent thrombosis.

Conclusions

In this larger-scale IPD NMA in STEMI patients, second-generation DES were superior to BMS with respect to long-term efficacy and safety outcomes. Second-generation DES were associated with a significant reduction of stent thrombosis compared with BMS and first-generation DES. Similar long-term outcomes were observed between DP-EES and BP-BES.

Acknowledgement/Funding

This study was funded by Biosensors International

P2817Efficacy and safety of ticagrelor monotherapy in patients with complex percutaneous coronary intervention: insights from the Global Leaders trial

Background/Introduction

Purpose

Methods

The Global Leaders trial recruited 15,991 patients treated by default with a biolimus A9-eluting stent, and randomised in a 1:1 ratio either to the experimental strategy (1-month dual antiplatelet therapy [DAPT] followed by 23-month ticagrelor monotherapy) or to the reference regimen (12-month DAPT followed by 12-month aspirin monotherapy). Complex PCI includes at least one of the following characteristics; left main and/or multivessel PCI, long stenting (defined as total stent length≥46mm), and bifurcation treatment with two stents. The present sub-analysis of the trial evaluated at two years the primary endpoint (composite of all-cause death and new Q-wave myocardial infarction [MI] centrally adjudicated with the Minnesota code). In addition, the patient-oriented composite endpoint (POCE) (composite of all-cause death, any stroke, any MI, and any revascularization) and the net adverse clinical events (NACE) (composite of POCE and Bleeding Academic Research Consortium [BARC] type 3 or 5 bleeding) were also evaluated at two years.

Results

Of 15,450 patients included in the present analysis, 5,188 (26.7%) patients underwent complex PCI. The experimental strategy, when compared with the reference one, had a significantly lower risk of the primary endpoint (3.56% vs. 5.33%, HR: 0.66; 95% CI: 0.51–0.86; p-value= 0.002; p-value for interaction= 0.019) in patients with complex PCI. Similarly, the experimental treatment was associated with a significantly reduced risk of POCE (14.41% vs. 16.88%, HR: 0.84; 95% CI: 0.74–0.97; p=0.016, p-value for interaction= 0.099) and NACE (15.77% vs. 18.37%, HR: 0.85; 95% CI: 0.74–0.97; p=0.014; p-value for interaction= 0.096). The reduction in ischemic events was predominantly observed in patients with 2 or more characteristics of complex PCI (Figure). In contrast, there was no significant difference in the risk of BARC type 3 or 5 bleeding between the two regimens (2.40% vs. 2.38%, HR: 1.01; 95% CI: 0.71–1.44; p-value=0.956; p-value for interaction= 0.935).

Central illustration

Conclusion

Together with other well-established clinical risk factors, the extent and complexity of stenting should be taken into account in tailoring antiplatelet regimens for secondary prevention. The 1-month DAPT followed by 23-month ticagrelor monotherapy reduced the ischemic events without increasing the risk of bleeding in patients who underwent complex PCI, when compared with the conventional DAPT.

Acknowledgement/Funding

The Global Leaders trial was supported by the resource from AstraZeneca, Biosensors, and The Medicines Company.

P2811Impact of ticagrelor monotherapy on two-year clinical outcomes in patients with long stenting: insights from the Global Leaders trial

Background/Introduction

Data on the efficacy and safety of different antiplatelet regimens are limited in patients with increasing total stent length (TSL).

Purpose

To evaluate the impact of the experimental strategy (1-month dual antiplatelet therapy [DAPT] followed by 23-month ticagrelor monotherapy) vs. the reference regimen (12-month DAPT followed by 12-month aspirin monotherapy) in patients with increasing TSL.

Methods

The present post-hoc analysis of the Global Leaders trial evaluated the primary endpoint (the composite of the all-cause death and new Q-wave myocardial infarction [MI]) at two years in patients with increasing TSL. In addition, the patient-oriented composite endpoint (POCE) (the composite of all-cause death, any stroke, any MI, and any revascularization) and the net adverse clinical events (NACE) (the composite of POCE and Bleeding Academic Research Consortium [BARC] type 3 or 5 bleeding) were also assessed.

Results

The cohort of 15,450 patients treated with a biolimus-eluting biodegradable polymer stents were included in this analysis. In the longer TSL group (≥46mm), the experimental strategy significantly reduced the risk of the primary endpoint (3.78% vs. 5.68%, hazard ratio (HR): 0.67, 95% confidence interval (CI): 0.49–0.90, p=0.008, P interaction=0.042) as well as POCE (14.57% vs. 18.11%, HR: 0.79, 95% CI: 0.67–0.92, p=0.003, P interaction=0.010) and NACE (16.07% vs. 19.64%, HR: 0.80, 95% CI: 0.69–0.93, p=0.004, P interaction=0.012) at two years. The risk of BARC type 3 or 5 bleeding at two years was similar between the two antiplatelet regimens.

KM in patients with long stenting

Conclusion

Ticagrelor monotherapy significantly reduced the risk of the primary endpoint, POCE and NACE with a similar risk of BARC type 3 or 5 bleeding at two years in patients with the longer TSL.

Acknowledgement/Funding

The Global Leaders trial was supported by unrestricted grants from AstraZeneca, Biosensors, and The Medicines Company. ECRI (European Cardiovascular R

P2812Ischemic efficacy and bleeding safety of ticagrelor monotherapy in patients with multivessel percutaneous coronary intervention: insights from the Global Leaders trial

Background/Introduction

The optimal duration of DAPT after coronary stent implantation remains a matter of debate and a novel antiplatelet regimen without an increased risk of bleeding while maintaining an anti-ischemic efficacy is of paramount importance in patients at higher risk of ischemia.

Purpose

The aim of the present sub-study of the Global Leaders trial is to evaluate the efficacy and safety of the experimental antiplatelet strategy (1-month dual antiplatelet therapy [DAPT] followed by 23-month ticagrelor monotherapy) vs. the reference regimen (12-month DAPT followed by 12-month aspirin monotherapy) in patients with multivessel percutaneous coronary intervention (PCI).

Methods

The Global Leaders trial enrolled 15,991 patients treated by default with a biolimus A-9 eluting stent. The present sub-study of the trial sought to evaluate the impact of the long-term ticagrelor monotherapy on the primary endpoint (composite of all-cause death and new Q-wave myocardial infarction [MI] centrally adjudicated with the Minnesota code) at two years. In addition, the patient-oriented composite endpoint (POCE) (composite of all-cause death, any stroke, any MI, and any revascularization) and the net adverse clinical events (NACE) (composite of POCE and Bleeding Academic Research Consortium [BARC] type 3 or 5 bleeding) were also evaluated at two years.

Results

A total of 15,845 patients was included in this analysis, of whom 3,576 patients received multivessel PCI. At two years, the experimental strategy significantly reduced a risk of the primary endpoint (the composite of all-cause death and new Q-wave myocardial infarction [MI]) (3.05% vs. 4.85%, HR: 0.62, 95% CI: 0.44–0.88, p=0.006, Pinteraction=0.031) in patients with multivessel PCI. Similarly, the experimental treatment had a significant risk reduction in the patient-oriented composite endpoint (POCE), defined as the composite of all-cause death, any stroke, any MI, and any revascularization (13.37% vs. 16.74%, HR: 0.78, 95% CI: 0.66–0.93, p=0.005, Pinteraction=0.020) and the net adverse clinical events (NACE), defined as the composite of POCE and Bleeding Academic Research Consortium [BARC] defined bleeding type 3 or 5 (14.65% vs. 18.38%, HR: 0.78, 95% CI: 0.66–0.92, p=0.003, Pinteraction=0.014) at two years. There was no significant difference in BARC type 3 or 5 bleeding (2.44% vs. 2.65%, HR: 0.92, 95% CI: 0.61–1.39, p=0.685, Pinteraction=0.754) at two years between the two regimens.

KM in patients with multivessel PCI

Conclusion

The present study has demonstrated the experimental antiplatelet strategy, when compared with the reference regimen, could potentially have a favourable balance between ischemic efficacy and bleeding safety in patients who underwent multivessel PCI.

Acknowledgement/Funding

The Global Leaders trial was supported by unrestricted grants from AstraZeneca, Biosensors, and The Medicines Company. ECRI (European Cardiovascular R

Sirolimus-eluting stents, bare metal stents or coronary artery bypass grafting for patients with multivessel disease including involvement of the proximal left anterior descending artery: analysis of the Arterial Revascularization Therapies study part 2 (ARTS-II)

OBJECTIVE

The The Arterial Revascularization Therapies Study (ARTS)-II trial found no differences in survival or overall adverse events between sirolimus-eluting stents (SES) and the surgical arm of ARTS-I. Nevertheless, existing data suggest that patients with disease of the proximal left anterior descending artery (LAD) may derive particular benefit from coronary artery bypass grafting (CABG). We therefore analysed the clinical outcome of patients in ARTS-I and ARTS-II with proximal LAD involvement.

DESIGN

Multicentre observational study.

SETTING

Forty-five European academic hospitals.

PATIENTS

Patients with multivessel coronary artery disease.

INTERVENTIONS

Patients in ARTS-II with proximal LAD disease treated with SES (289/607, 48%) were compared with 187/600 (31%) bare metal stent patients (ARTS-I BMS) and 206/605 (34%) surgical patients (ARTS-I CABG) with proximal LAD involvement from ARTS-I.

MAIN OUTCOME MEASURES

Major adverse cardiac and cerebrovascular events after 3 years.

RESULTS

The Arterial Revascularization Therapies study part 2 (ARTS-II) subgroup had better survival than both ARTS-I groups (ARTS-II 98.6% vs ARTS-I BMS 95.7%, p = 0.05 and vs ARTS-I CABG 94.7%, p = 0.01) and lower rates of the hard clinical composite endpoint of death or non-fatal myocardial infarction (ARTS-II 3.1% vs ARTS-I BMS 9.6%, p = 0.002 and vs ARTS-I CABG 9.7%, p = 0.002). Although the ARTS-I CABG patients had a lower need for repeat revascularisation than ARTS-II (5.3% vs 13.1%, p = 0.002), the overall composite adverse event rates (death, myocardial infarction, stroke or any repeat revascularisation) were not significantly different between the ARTS-I CABG and ARTS-II patients (15.0% vs 18.0%, p = 0.4).

CONCLUSIONS

SES are not inferior to CABG or bare metal stents for the treatment of patients with multivessel coronary disease including involvement of the proximal LAD.

Pharmacokinetics and consistency of pericardial delivery directed to coronary arteries: direct comparison with endoluminal delivery

BACKGROUND AND HYPOTHESIS

Pharmacologic modulation of the contents of the pericardial space has been shown to influence the response of coronary arteries to balloon injury. Endoluminal (EL) local delivery of various drugs into coronaries has been found to be limited by short residence time, as well as by highly variable deposited agent concentration. We hypothesized that compounds placed into the pericardial space (P) would penetrate into coronary tissue with greater consistency than seen after EL delivery and provide for prolonged coronary exposure to agents.

METHODS AND RESULTS

125I-labeled basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), albumin, or 131I-labeled diazeniumdiolated albumin (NONO-albumin) were delivered as model/therapeutic proteins into the porcine pericardial space (n = 15 pigs) or into coronaries using an EL delivery catheter (n = 48 arteries). In subjects receiving 125I-labeled proteins, the delivery target or mid-regions of the left anterior descending (LAD) and left circumflex (LCx) arteries were harvested at 1 h or 24 h for gamma-counting and autoradiography, and fractional intramural delivery (FID) or retention measured as percent agent in 100 mg artery/agent in infusate for both time points. In the animals receiving 131I-labeled NONO-albumin, serial gamma imaging was employed to evaluate the rate of redistribution in individual animals following either pericardial or endoluminal delivery. At 1 h, FID values ranged from 0.00064 to 0.0052% for P delivery (median 0.0022%), and from 0.00021 to 6.7 for EL delivery (median 0.27%). At 24 h, FID values ranged from 0.00011 to 0.003 for P delivery (median 0.0013), and from 0.0002 to 1.4 for EL delivery. The estimated T1/2 for bFGF redistribution from the vascular tissue was 22 h (P) and 7 h (EL), respectively, while the directly determined T1/2 values for NONO-albumin redistribution from the delivery region were 22.2 h (P) and 2.5 h (EL).

CONCLUSIONS

These data show that pericardial fluid contents can access coronary arteries with intramural concentrations which typically vary by 10-15-fold, while EL delivery results in a remarkably wide intramural concentration range with up to 33,000-fold variability. The apparent redistribution rate is more rapid following EL delivery, possibly due to sustained diffusive tissue loading from the pericardial space. Pericardial delivery appears to offer substantial advantages over EL administration with respect to residence time and reproducibility.

Advantages of short-lived positron-emitting radioisotopes for intracoronary radiation therapy with liquid-filled balloons to prevent restenosis

Balloon catheters filled with liquid radioisotopes provide excellent dose homogeneity for intracoronary radiation therapy but are associated with risk for rupture or leakage. We hypothesized that the safety of liquid-filled balloons may be improved once positron emitters with half-lives below 2 h are used instead of the high-energy beta-emitters 166Ho, 186Re, or 188Re, all of which have a longer half-life of at least 17 h.

METHODS

To support this concept, the suitability of 18F (half-life, 109.8 min), 68Ga (half-life, 67.6 min), 11C (half-life, 20.4 min), 13N (half-life, 9.97 min), and 15O (half-life, 2.04 min) for intracoronary radiation therapy was evaluated. Potential tissue penetration of positron radiation was assessed in a series of phantom experiments using Gafchromic film. Antiproliferative efficacy of positrons emitted by 68Ga was investigated in vitro using cultured bovine aortic smooth muscle cells (BASMCs), and was compared with gamma-radiation emitted by 137Cs. To characterize the remaining risk, we estimated radiotoxicity after accidental intravascular balloon rupture on the basis of tabulated isotope-specific doses (ICRP 53) and compared these values with 188Re.

RESULTS

Half-dose depth of tissue penetration measured in phantom experiments was 0.29 mm for 18F, 0.42 mm for 11C, 0.54 mm for 13N, 0.79 mm for 15O, and 0.9 mm for 68Ga. Irradiation of cultured BASMCs with positron radiation (68Ga) induced dose-dependent inhibition of proliferation with complete proliferative arrest at doses exceeding 6 Gy. ED(50) and ED(80) were 2.5 +/- 0.4 Gy (mean +/- SD) and 4.4 +/- 0.8 Gy, respectively. Antiproliferative efficacy was equal to that of the 662-keV gamma-radiation emitted by 137Cs (ED(50), 3.8 +/- 0.2 Gy; ED(80), 8.0 +/- 0.3 Gy). Estimates made for patient whole-body and organ doses were generally below 50 mSv/1.85 GBq for all investigated positron emitters. The same dose estimates for 188Re were 6-20 fold higher.

CONCLUSION

Among the studied radioisotopes, 68Ga is the most attractive source for liquid-filled balloons because of its convenient half-life, sufficient positron energy (2.92 MeV), documented antiproliferative efficacy, and uncomplicated availability from a radioisotope generator. The safety profile for 68Ga is significantly better than that of 188Re, which suggests this radioisotope should be evaluated further in preclinical studies.

Liquid-filled balloon brachytherapy using (68)Ga is effective and safe because of the short 68-minute half-life: results of a feasibility study in the porcine coronary overstretch model

BACKGROUND

Liquid-filled balloons for coronary brachytherapy provide significant advantages over solid sources in dose homogeneity but carry the risk of life-threatening radiointoxication after balloon rupture and laboratory contamination in case of a spill. We hypothesized that the positron emitter (68)Ga, with a half-life of only 68 minutes, was well suited to overcome these safety obstacles while providing full therapeutic efficacy.

METHODS AND RESULTS

The feasibility, efficacy, and safety of (68)Ga liquid-filled balloon brachytherapy were investigated in the porcine coronary overstretch model. Four groups of 5 balloon-induced coronary lesions were irradiated with 8, 12, 16, and 24 Gy targeted to the adventitia. Ten unirradiated lesions served as controls. Segments treated with 16 or 24 Gy exhibited marked suppression of neointimal proliferation at 28-day follow-up, with quantitative parameters of intraluminal proliferation reduced to <20%. This beneficial effect was not compromised by untoward edge effects. Uninjured but irradiated vessels did not show histological signs of radiation damage. The (68)Ga whole-body dose due to balloon rupture was estimated to be 5 rem/50 mCi treatment activity and compared favorably with that of (188)Re (78 rem/50 mCi).

CONCLUSIONS

(68)Ga positron radiation suppresses neointimal proliferation at doses of 16 and 24 Gy. This biological efficacy, coupled with the attractive safety profile, suggests the selection of (68)Ga as an attractive isotope for liquid-filled balloon brachytherapy.

Experimental validation of a new coronary guide wire labeled with rubidium 81/krypton 81m for continuous assessment of myocardial blood flow

BACKGROUND

The rubidium 81/krypton 81m method was suggested for assessment of myocardial blood flow (MBF) three decades ago. This study investigates the novel concept of using 81Rb-/81mKr-labeled coronary guide wires with wire-attached 81Rb activity and diffusable 81mKr gas for assessment of lesion-specific impairment of MBF by evaluation of the 81Rb/81mKr activity ratio. The feasibility of wire production is tested, and application of the method is investigated in the canine model.

METHODS AND RESULTS

Conventional coronary guide wires for angioplasty (0.014 in) were labeled with radioactive 81Rb/81mKr by ion bombardment of the wire tip. A total of 16 of the 18 wires labeled in series showed successful 81Rb fixation in combination with free 81mKr gas diffusability during quality control measurements. The suitability of the wires to assess MBF in combination with an external gamma ray detector was investigated in open-chested dogs. Electromagnetic measurement of coronary blood flow (CBF) was used as reference, providing a signal that is directly linked to volumetric MBF. The 81Rb/81mKr ratio tracked changes in CBF reliably in all 6 dogs. The found linear dependence of measured 81Rb/81mKr count rates on measured CBF supports the modeling assumptions made to apply the theoretic basis of the 81Rb/81mKr technique to 81Rb-labeled coronary guide wires.

CONCLUSION

81Rb-/81mKr-labeled coronary guide wires provide a signal that indicates volumetric MBF directly. This unique capability may qualify the technique as a valuable tool for research purposes and as an attractive method for invasive cardiology at centers where the logistic arrangements for short-lived isotope supply are provided.

High resolution ECG and left ventricular volume after acute myocardial infarction

The presence of ventricular late potentials (LPs) early after acute myocardial infarction (AMI) was recently reported to correlate with left ventricular dilatation subsequent to AMI. We assessed prospectively the relationship between LP (time domain) in the late phase of AMI and left ventricular end-diastolic volume (EDV) measured by equilibrium radionuclide angiocardiography 4 weeks and 12 months after AMI. In 80 consecutive patients 4 weeks and 12 months after thrombolytic therapy for AMI, LP and EDV were determined (EDV1, EDV2). There was no significant correlation between QRS duration (r = 0.18), RMS40 (r = 0.08), or LAS40 (r = 0.1) and EDV1 or EDV2 in patients with or without LP at baseline. In both groups (patients with [n = 15] and without LP [n = 65]), EDV1 and EDV2 were comparable (128 +/- 32 mL vs 126 +/- 35 mL; 114 +/- 40 mL vs 117 +/- 36 mL; P = NS). In addition, there was no significant difference between EDV1 and EDV2 in patients who developed new LP (n = 6) or lost LP (n = 9) 12 months after AMI. In contrast to LP in the very early phase after AMI, there seems to be no significant correlation between the high resolution ECG in the late phase after thrombolytic therapy for AMI and left ventricular EDV.

Myocardial metabolic imaging by means of fluorine-18 deoxyglucose/technetium-99m sestamibi dual-isotope single-photon emission tomography

The detection of preserved glucose uptake in hypoperfused dysfunctional myocardium by fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) represents the method of choice in myocardial viability diagnostics. As the technique is not available for the majority of patients due to cost and the limited capacity of the PET centres, it was the aim of the present work to develop and test FDG single-photon emission tomography (SPET) with the means of conventional nuclear medicine. The perfusion marker sestamibi (MIBI) was used together with the metabolic tracer FDG in dual-isotope acquisition. A conventional SPET camera was equipped with a 511-keV collimator and designed to operate with simultaneous four-channel acquisition. In this way, the scatter of 18F into the technetium-99m energy window could be taken into account by a novel method of scatter correction. Thirty patients with regional wall motion abnormalities at rest were investigated. The results of visual wall motion analysis by contrast cine-ventriculography in nine segments/heart were compared with the results of quantitative scintigraphy. The scintigraphic patterns of MIBI and FDG tracer accumulation were defined as normal, matched defects and perfusion-metabolism mismatches. Spatial resolution of the system was satisfactory, with a full width at half maximum (FWHM) of 15.2 mm for 18F and 14.0 mm for 99mTc, as measured by planar imaging in air at 5 cm distance from the collimator. Image quality allowed interpretation in all 30 patients. 88% of segments without relevant wall motion abnormalities presented normal scintigraphic results. Seventy-five akinetic segments showed mismatches in 27%, matched defects in 44% and normal perfusion in 29%. We conclude that FDG-MIBI dual-isotope SPET is technically feasible with the means of conventional nuclear medicine. Thus, the method is potentially available for widespread application in patient care and may represent an alternative to the 201Tl reinjection technique.

Myocardial perfusion measured by dual-isotope acquisition of 81rubidium/81mkrypton: an experimental verification of the method

PURPOSE

The purpose of the study was to verify that the 81Rubidium/81mkrypton (81Rb/81mKr) method allows the quantitative measurement of myocardial perfusion.

PRINCIPLE

The potassium analogous cation 81Rb is accumulated in the myocardium by the cell membrane-bound Na-K-ATPase. After accumulation an intracellular equilibrium establishes between 81Rb and its radioactive daughter nuclide 81mKr. The flow-sensitive method evaluates the disturbance of this equilibrium by perfusion which washes out the short-lived diffusable daughter nuclide 81mKr while the mother nuclide 81Rb remains cell-bound.

METHODS

Isolated rabbit hearts were prepared in a modified Langendorff technique which allowed quantitative collection of the coronary sinus efflux. The myocardium was labeled with pure 81Rb by bolus injection into the aortic cannula. Spectroscopic measurements of 81Rb and 81mKr gamma radiation were performed using a germanium detector. Perfusion was varied in the range between 0 and 4 ml/min/g. The activity ratio 81Rb/81mKr was determined and compared with coronary sinus effusion.

RESULTS

81Rb/81mKr activity ratio was closely related (r = 0.98) to perfusion as described by the predicted equation Rb/Kr = (F/2.96 P) + 1. (Rb/Kr = activity ratio between 81Rb and 81mKr in the myocardium; F = myocardial perfusion (ml/min/g); P = partition coefficient (myocardium/perfusate) for Krypton gas). The constant P was found to be 1.14 +/- 0.06 (mean +/- SEM). No saturation of this ratio at high flow rates was observed.

CONCLUSION

The activity ratio 81Rb/81mKr is a valid quantitative measure for myocardial perfusion in isolated hearts. The main limitation of the method before application in man is the correction of the different gamma ray tissue absorption of both nuclides.

Cineradiography for determination of normal and abnormal function in mechanical heart valves

To determine the diagnostic value of cineradiography of mechanical heart valves, 112 cinefluoroscopic studies were performed in 76 patients with 95 valve prostheses (caged ball or disk valves, tilting disk and bileaflet valves). A patient group (n = 45) presenting with clinical or echocardiographic findings suggestive of valve-related complications was compared with a control group (n = 31) without such symptoms. Disk-opening angles (mean +/- SD) for Medtronic Hall aortic valves were found to be significantly smaller (62.8 +/- 11.1 degrees) in patients than in control subjects (73.9 +/- 1.6 degrees; p < 0.05). Tissue ingrowth or thrombus formation, or both, demonstrated in 3 patients on subsequent reoperation, are considered as the main cause of incomplete or asymmetric disk opening. Opening and closing times did not differ significantly between patients and control subjects. Besides abnormal valve motion, structural defects such as strut fracture or leaflet escape could be rapidly detected by cineradiography if x-ray projections according to the particular valve design were used. Together with quantitative Doppler echocardiographic and clinical data, this method can help to give specific answers if the question is to either confirm or exclude imminent or acute valve malfunction. Thus, modern cineradiography is a highly valuable noninvasive diagnostic tool for both rapid management of emergency cases and routine follow-up of patients with mechanical heart valves.

[Third replacement of the tricuspid valve in combined aortic-tricuspid defect]

The implantation of valvular prostheses in tricuspid position is problematic due to the slow blood flow in the low-pressure system with the risk of valvular thromboses. Today there are prostheses with supportable low transvalvular gradients; nevertheless, the risk of valvular thromboses is, in spite of anticoagulation, increased by using mechanical prostheses in tricuspid position. We report on a 51-year-old woman in whom a dysfunction of the Starr Edwards ball prosthesis 15 years after its implantation in the tricuspid position was diagnosed. The prosthesis, which was unable to function due to connective tissue proliferation, was replaced by a St. Jude Medical prosthetic valve, which also presented a disturbed function a few days after the implantation. Because of a suspected valve thrombosis the patient was treated with rt-PA-lysis which proved to be ineffective. Thus it was inevitable to implant a third tricuspid valve; this time a bioprosthesis was used.

[Nuclear medicine assessment of renal function in beagles before and after extracorporeal percutaneous lithotripsy with a piezoelectric instrument system]

High energy sound pulses which are generated piezoelectrically can be used for extracorporal lithotripsy as an alternative to shock-waves. Since several years a lithotripter for renal concrements based on piezoelectrical oscillators has been developed at the Department for Urology in Homburg/Saar; W.Germany. The present paper describes animal experiments which have been carried out with Beagle-dogs in order to prove that the sound pulses used for lithotripsy do not affect renal function. This function is measured by methods of nuclear medicine (131J-Hippuran Clearance with a modified evaluation). In addition it is evaluated by 111In labelled leucocytes if inflammatory processes in the kidney are suspected. It could be demonstrated that no detremental effects on the kidneys can be detected even with the most sensitive methods of nuclear medicine.

[Disintegration of kidney calculi by piezoelectrically generated high-energy sound waves. Physical principles and experimental studies]

The recently developed equipment for extracorporeal piezoelectric lithotripsy (EPL) represents an improvement concerning the shock-wave-induced disintegration of urinary calculi. While the usual spark gap transmitter needs a focusing reflector, the piezoelectric lithotriptor is based on a self-focusing spherical bowl transmitter. The stone is detected exclusively by ultrasound. For this purpose, an integrated sector scanner is used as well as the high-energy sound transmitter itself. With the piezoelectrically generated high-energy sound pulses we have succeeded in completely disintegrating implanted stones in the renal pelvis of dogs without injuring the morphology or function of the exposed kidneys.