Outcomes of endovascular management of the aorta in connective tissue disorders

Background

Endovascular management of type B aortic dissection has been well established and accepted in the community. However, due to the lack of information on long-term outcome, endovascular management remains controversial in the setting of connective tissue disorders such as Marfan syndrome. Although surgical repair is recommended in type B aortic dissection with connective tissue disorders, recent studies demonstrated both feasibility and safety of endovascular interventions in those patients at least short term.

Purpose

Single centre experience and documentation of long-term outcomes after endovascular management of aortic conditions in patients with connective tissue disorders.

Methods

All patients with genetic confirmation of connective tissue disorders who underwent endovascular repair of the thoracic aorta were identified and evaluated retrospectively. Perioperative, procedure-specific and follow-up data were extracted from medical records of a structured surveillance program.

Results

Between 2002 and 2020, 18 patients were identified having undergone TEVAR procedures and protocol follow-up. The median age was 35.5 (IQL 30.0 – 42.7), and 12 (66.7%) were males; median ACEF II score was 0.6 (IQL 0.5 – 0.925).

This cohort comprised 15 (83.3%) patients with genetically confirmed Marfan syndrome, two (11.1%) with Loeys-Dietz, and one (5.6%) with Ehlers-Danlos syndrome. Of these, 13 (72.2%) patients had undergone aortic root or aortic root/ascending aorta replacement independently in the past. The indication for a TEVAR procedure was seen in one case for degenerative aneurysmal disease (5.6%), in one case for elephant trunk stenosis (5.6%), in five cases for residual aortic dissection (27.8%), and in 11 cases for new type B dissection (61.1%).

The most frequently used stent-graft was Valiant™ (Medtronic) in 10 cases (55.6%), followed by TAG® (Gore®) in four cases (22.2%), Zenith® (COOK®) in two cases (11.1%), and for Relay® (Bolton) and Sinus-XL® (Optimed) in one case each (5.6%). The average total covered length was 192.2±40.2 mm.

Median follow-up duration was 77.5 months (IQR 35.8 - 131); three (16.7%) cases revealed failure of TEVAR and led to conversion to open surgery. Two patients (11.1%) had died including one patient in the perioperative phase. At the last follow-up, complete thrombosis of the false lumen was observed in 14 cases (82.3%), and 15 cases (88.2%) showed no aortic expansion or progression during the follow-up period resulting in an overall endovascular success rate of 72.2%.

Conclusion

Thoracic endovascular aortic repair can be performed for selected patients with connective tissue disorders at relatively low long-term mortality and morbidity. With improved devices and technical skills, mid- and long-term surveillance revealed promising outcomes and a low rate of aneurysmal degeneration. Structured surveillance remains crucial to detect emerging late complications and to accumulate more long-term data.

Funding Acknowledgement

Type of funding sources: None.

Impact of COVID-19 pandemic on surgical care of patients with acute aortic conditions

Background

The outbreak of COVID-19 pandemic catastrophically interrupted medical care systems causing substantial decrease in the admission of patients and consecutively a sharp decline in the number of surgeries and interventions. In several European countries, the nationwide lockdown severely restricted movement which may have contributed to this phenomenon on top of anxiety of patients to contract COVID-19 when admitted to hospital.

Purpose

The aim of this analysis was to evaluate the impact of the COVID-19 pandemic onto acute and elective thoracic aortic surgeries and interventions and to compare the data with the same period in 2019 in a single aortic centre.

Methods

Information on admission and surgery/intervention was extracted from hospital electronic record system. Patients who were admitted for treatment of aortic conditions between January 1st to June 30th both in 2019 and 2020 were identified and selected for this analysis. The time from referral to admission and surgery/intervention was noted for service delay analysis. Aortopathies were classified as type A aortic dissection, type B aortic dissection, aortic aneurysm and others. In a daily central hub meeting, urgency was defined as emergent (operation required before the next working day), urgent (operation needed within 48 hours), and elective. Patients' condition and comorbidities were represented by ACEF II score.

Results

Total case volume of 81 in 2019 reference period was reduced to 70 in 2020 (−14%). Elective cases significantly declined from 59 (72.8%) in 2019 to 30 (42.8%) in 2020 (−49%). Urgent and emergent cases were performed more frequently in 2020 with 40 cases versus 22 in 2019 (+45%).

The ACEF II score showed no difference for patients in both periods (2.1±1.9 vs. 2.5±2.1, p=0.221), however, a trend to higher ACEF II score in 2020 consistent with a higher proportion of urgent and emergent cases.

The overall in-hospital delay (from admission to surgery) was not significant affected with 1 (IQR 1–2) versus 1 (IQR 0–2); p=0.991. However, with the official declaration of a pandemic and introduction of restrictions, no in-hospital delay was documented.

In-hospital mortality was observed lower in 2019 as compared in 2020 (6.1% vs 11.4%, P=0.251).

Conclusion

The first wave of COVID-19 pandemic disrupted the aortic service, however, acute care for urgent thoracic aortic conditions and subsequent procedures even increased compared to 2019 as a result of both centralised allocation system and decline of elective cases. Acute aortic syndromes were managed despite COVID-19 according to current guidelines.

Funding Acknowledgement

Type of funding sources: None.

Position paper nuclear cardiology: Update 2008

Nuclear cardiology is well established in clinical diagnostic algorithms for many years. This is an update 2008 of the first common position paper of the German Association of Nuclear Medicine and the German Association of Cardiology, Heart and Circulation Research published in 2001 aiming at an overview of state-of-the-art scintigraphic methods.

[Optical coherence tomography of coronary arteries--a novel intravascular imaging modality]

Optical coherence tomography (OCT) is the latest intravascular imaging modality for the investigation of coronary arteries. It can be used in patients with stable coronary artery disease as well as in patients with acute coronary syndrome. Its almost microscope-like resolution of 10-20 μm (10-times greater than intravascular ultrasound) gives us the most detailed insight into the coronary artery wall in vivo so far.Optical coherence tomography can be used for accurate qualitative and quantitative assessment of stenoses in stable coronary artery disease and accurate guidance of percutaneous coronary interventions as well as accurate postprocedural control. In patients with acute coronary syndrome it can be used for the detection of culprit of the culprit lesion (vulnerable plaque) which allows the operator to cover not only angiographically tightest stenosis (angiographic culprit lesion, caused in most cases by thrombus only) but most importantly the vulnerable plaque, which led to the acute event, as well. Furthermore, optical coherence tomography allows accurate assessment of thrombotic burden, stent apposition/malapposition, edge dissections and tissue prolaps or thrombus protrusions throught stent struts, etc.

Bivalirudin use in patients undergoing percutaneous coronary intervention for acute myocardial infarction. Insights from the prospective, multi-centre EUROVISION registry

BACKGROUND

The effectiveness of bivalirudin in patients undergoing percutaneous coronary intervention for acute myocardial infarction has been tested in clinical trials, but its use in a real-world scenario has never been reported.

METHODS

From the total number of patients enrolled in the EUROVISION registry, 678 subjects affected by ST-elevation myocardial infarction were selected and included in the analysis. Posology and usage patterns of bivalirudin, as evaluated by dose and time of drug bolus and infusion administered, were evaluated. The 30-day outcome has been assessed by efficacy and safety endpoints.

RESULTS

All patients received an initial intravenous bolus of bivalirudin (0.70±0.25 mg/kg) followed by an infusion (1.58±0.47 mg/kg/h; duration: 60 [30, 107] min) in 99.3% of cases. An additional bolus (0.49±0.06 mg/kg) was administered in 9.3% of patients. Bivalirudin infusion was prolonged after procedure in 62.2%. Death occurred in 2.1% of patients, non-fatal myocardial reinfarction in 0.3%, unplanned revascularization in 0.6% and non-fatal stroke in 0.4%. Acute stent thrombosis was not observed. Major bleeding occurred in 1.5% of patients.

CONCLUSIONS

Bivalirudin usage in the setting of primary PCI provided excellent results in terms of 30-day outcome even in a real-world population.

[Dynamic left ventricular outflow tract obstruction in pulmonary embolism]

Left ventricular hypertrophy, dehydration, sepsis, vasodilatation, excessive sympathetic stimulation, pericardial tamponade and surgical treatment of the atrioventricular valve are known causes of left ventricular outflow tract (LVOT) obstruction. We report the rare case of a patient who developed dynamic LVOT obstruction as a complication of acute pulmonary embolism.

Penetrating aortic ulcer, intramural hematoma, acute aortic syndrome: when to do what

Acute aortic syndrome (AAS) is a modern term to describe interrelated emergency aortic conditions with similar clinical characteristics and challenges. These conditions include aortic dissection, intramural hematoma (IMH), and penetrating aortic ulcer (PAU). Population-based studies suggest that the incidence of aortic dissection ranges from 2.6-3.5 cases per 100,000 person/year; hypertension and a variety of genetic disorders with altered connective tissue are the most prevalent risk conditions. One in eight patients diagnosed with acute aortic dissection has either an IMH or a PAU. Pain is the most commonly presenting symptom of acute aortic syndrome and should prompt immediate attention including diagnostic imaging modalities (such as multislice computed tomography, transesophageal ultrasound, or magnetic resonance imaging). IMH and PAU need a specific therapeutic approach, because without treatment they have a very poor evolution, are unpredictable and can be worse than acute aortic dissection. All patients must receive the best medical treatment available at admission. High-risk but asymptomatic patients with IMH and PAU can probably be followed-up without intervention. All symptomatic patients will need treatment. In many of these patients, a direct surgical approach is often prohibitive, due to age and multiple comorbidities. Endovascular treatment offers superior results and is becoming a recognized indication for patients. Irrespective of treatment modality, a close follow-up is mandatory in order to detect disease progression.

[Therapy strategies for acute coronary syndrome and after coronary interventions. Antiplatelet agents and anticoagulants]

There is ongoing development of new therapeutic regimens in the use of antithrombotic agents and anticoagulants focussing on acute coronary syndrome (ACS) with an increasing impact on current guidelines over the last years. This was especially accompanied by an increase in innovative percutaneous coronary interventional (PCI) methods in patients with ACS, non-ST-segment elevation myocardial infarction (NSTEMI) or ST-segment elevation myocardial infarction (STEMI) with a need for therapeutics with more sufficient and effective antiplatelet action. On the other hand, newer direct and indirect thrombin inhibitors with primary use in prevention and therapy of thromboembolic events have been shown to have beneficial and even superior effects in ACS with or without PCI. The current review aims to report on the evidence-based use of approved antithrombotic agents and anticoagulants in ACS with special focus on PCI according to the actualized European guidelines.

The importance of the collateral circulation for myocardial survival

In acute coronary occlusion the survival time of ischemic myocardium depends critically upon collateral blood flow and on oxygen uptake at the moment of, and during, occlusion. There are good reasons to believe that ischemic myocardium provides the stimulus for near-maximal vasodilation of collateral blood vessels. Under these conditions the determinants of collateral blood flow are: a) the anatomically fixed hydraulic resistance of the collaterals proper, b) the arterial driving pressure, c) extravascular resistance (radial stress, pressure transmission across the LV wall, tissue pressure) and d) size of the ischemic bed. Under ideal conditions (maximal dilation of collaterals) overall collateral resistance is 3.5 resistance units, i.e. theoretically a perfusion pressure of 350 mmHg is needed to drive 100 ml of blood per minute through 100 g of tissue. Small ischemic beds receive a relatively larger amount of collateral flow and vice versa. This delays necrosis (but does not prevent it) following occlusion of small coronary arteries. The reason for this is the more favorable ratio of epicardial circumference (of the ischemic area) to ischemic volume because canine collaterals are exclusively located on the epicardial surface.-Tissue pressure in acute occlusion is distributed in such a way that subendocardial collateral flow is lower than subepicardial flow. This leads to an earlier onset of irreversible damage in the subendocardium, earlier damage to subendocardial microvessels, i.e. earlier subendocardial no-reflow phenomenon. Flow "offered" to but not "taken" by the subendocardium is at the disposal of the subepicardium which thereby increases its chances of survival. As a rule subendocardial flow decreases as a function of time after occlusion and subepicardial flow increases. In certain cases even subepicardial flow is too low shortly after occlusion. In this case it decreases further with time and a truly transmural infarct develops.

NC100100, a new echo contrast agent for the assessment of myocardial perfusion--safety and comparison with technetium-99m sestamibi single-photon emission computed tomography in a randomized multicenter study

BACKGROUND AND HYPOTHESIS

Myocardial contrast echocardiography using second-generation agents has been proposed to study myocardial perfusion. A placebo-controlled, multicenter trial was conducted to evaluate the safety, optimal dose, and imaging mode for NC100100, a novel intravenous second-generation echo contrast agent, and to compare this technique with technetium-99m sestamibi (MIBI) single-photon emission computed tomography (SPECT).

METHODS

In a placebo-controlled, multicenter trial, 203 patients with myocardial infarction > 5 days and < 1 year previously underwent rest SPECT and MCE. Fundamental and harmonic imaging modes combined with continuous and electrocardiogram-- (ECG) triggered intermittent imaging were used. Six dose groups (0.030, 0.100, and 0.300 microliter particles/kg body weight for fundamental imaging; and 0.006, 0.030, and 0.150 microliter particles/kg body weight for harmonic imaging) were tested. A saline group was also included. Safety was followed for 72 h after contrast injection. Myocardial perfusion by MCE was compared with myocardial rest perfusion imaging using MIBI as a tracer.

RESULTS

NC100100 was well tolerated. No serious adverse events or deaths occurred. No clinically relevant changes in vital signs, laboratory parameters, and ECG recordings were noted. There was no significant difference between adverse events in the NC100100 (25.7%) and in the placebo group (17.9%, p = 0.3). Intermittent harmonic imaging using the intermediate dose was superior to all other modalities, allowing the assessment of perfusion in 76% of all segments. Eighty segments (96%) with normal perfusion by SPECT imaging also showed myocardial perfusion with MCE. However, a substantial percentage of segments (61-80%) with perfusion defects by SPECT imaging also showed opacification by MCE. This resulted in an overall agreement of 66-81% and a high specificity (80-96%), but in low sensitivity (20-39%) of MCE for the detection of perfusion defects.

CONCLUSION

NC100100 is safe in patients with myocardial infarction. Intermittent harmonic imaging with a dose of 0.03 microliter particles/kg body weight can be proposed as the best imaging protocol. Myocardial contrast echocardiography with NC 100100 provides perfusion information in approximately 76% of segments and results in myocardial opacification in the vast majority of segments with normal perfusion as assessed by SPECT. Although the discrepancies between MCE and SPECT with regard to the definition of perfusion defects requires further investigation, MCE with NC 100100 is a promising technique for the noninvasive assessment of myocardial perfusion.

[Position paper nuclear cardiology: update 2008]

Nuclear cardiology is well established in clinical diagnostic algorithms for many years. This is an update 2008 of the first common position paper of the German Association of Nuclear Medicine and the German Association of Cardiology, Heart and Circulation Research published in 2001 aiming at an overview of state-of-the-art scintigraphic methods.

Accuracy and feasibility of contrast echocardiography for detection of perfusion defects in routine practice: comparison with wall motion and technetium-99m sestamibi single-photon emission computed tomography. The Nycomed NC100100 Investigators

OBJECTIVES

We sought to assess the feasibility and accuracy of myocardial contrast echocardiography (MCE) using standard imaging approaches for the detection of perfusion defects in patients who had a myocardial infarction (MI).

BACKGROUND

Myocardial contrast echocardiography may be more versatile than perfusion scintigraphy for identifying the presence and extent of perfusion defects after MI. However, its reliability in routine practice is unclear.

METHODS

Fundamental or harmonic MCE was performed with continuous or triggered imaging in 203 patients with a previous MI using bolus doses of a perfluorocarbon-filled contrast agent (NC100100). All patients underwent single-photon emission computed tomography (SPECT) after the injection of technetium-99m (Tc-99m) sestamibi at rest. Quantitative and semiquantitative SPECT, wall motion and digitized echocardiographic data were interpreted independently. The accuracy of MCE was assessed for detection of segments and patients with moderate and severe sestamibi-SPECT defects, as well as for detection of patients with extensive perfusion defects (>12% of left ventricle).

RESULTS

In segments with diagnostic MCE, the segmental sensitivity ranged from 14% to 65%, and the specificity varied from 78% to 95%, depending on the dose of contrast agent. Using both segment- and patient-based analysis, the greatest accuracy and proportion of interpretable images were obtained using harmonic imaging in the triggered mode. For the detection of extensive defects, the sensitivity varied from 13% to 48%, with specificity from 63% to 100%. Harmonic imaging remained the most accurate approach. Time since MI and SPECT defect location and intensity were all determinants of the MCE response. The extent of defects on MCE was less than the extent of either abnormal wall motion or SPECT abnormalities. The combination of wall motion and MCE assessment gave the best balance of sensitivity (46% to 55%) and specificity (82% to 83%).

CONCLUSIONS

Although MCE is specific, it has limited sensitivity for detection of moderate or severe perfusion defects, and it underestimates the extent of SPECT defects. The best results are obtained by integration with wall motion. More sophisticated methods of acquisition and interpretation are needed to enhance the feasibility of this technique in routine practice.

Results of transmyocardial laser revascularization in non-revascularizable coronary artery disease after 3 years follow-up [ssee comments]

BACKGROUND

Transmyocardial laser revascularization is a new therapeutic option for end-stage coronary artery disease if no other cardiological or cardiosurgical intervention is possible. Data are few on how patients fare after more than 1 year follow-up.

METHODS AND RESULTS

From a total of 157 patients who were suggested for transmyocardial laser therapy in the years 1995-1997, 126 were judged to have non-revascularizable coronary artery disease (mean age 61.9 +/- 14 years, 80% men, mean left ventricular ejection fraction 46.2 +/- 17.1%). Sixty-six patients had a good clinical response to intensification of the antianginal therapy and were therefore treated further medically. In 60 patients with refractory angina, sole transmyocardial laser revascularization without cardiopulmonary bypass or additional grafts was performed. The transmyocardial laser revascularization group was 32% female; 78.3% patients had had bypass operations; the mean left ventricular ejection fraction was 53.6 +/- 15%. Eighty five percent of the transmyocardial laser revascularization patients had demonstrable ischaemic regions, as visualized by dipyridamol-MIBI scintigraphy. The percentage of patients with some hibernating myocardium in positron emission tomography studies was 70%. Good early relief of angina symptoms was experienced by patients who had undergone laser treatment. After 3 months the Canadian Cardiovascular Society class fell from 3.31 +/- 0.51 to 1.84 +/- 0.77 in 49 patients (P < 0.0001), but increased in the total group to 2.02 +/- 0.92 after 6 months (n = 47), to 2.26 +/- 0.99 after 1 year (n = 42), to 2.47 +/- 1.11 after 2 years (n = 38) and to 2.58 +/- 0.9 after 3 years (n = 19). MIBI/positron emission tomography data at rest and after 6 months was worse in patients in whom pre- and postoperative studies were complete (n = 22). The peri-operative mortality was 12% (n = 7: peri-operative myocardial infarction, low output syndrome, arrhythmia). Mortality after 1 and 3 years was 23% and 30%, respectively. The risk of transmyocardial laser revascularization was significantly elevated in patients with left ventricular ejection fraction < 40%. Late deaths (n = 9) were due to sudden arrhythmias or pump failure. There was a high rate of cardiac events and reinterventions in the transmyocardial laser revascularization group, including percutaneous transluminal coronary angioplasty in newly developed lesions (n = 7), valve replacement (n = 2), need for intermittent urokinase therapy (n = 5) and heart transplantation (n = 2).

CONCLUSION

Fifty percent of patients with non-revascularizable coronary artery disease submitted for transmyocardial laser revascularization can be stabilized medically. Transmyocardial laser revascularization led to a rapid early relief of symptoms, but with a trend towards worsening over time and showed a high peri-operative risk (> 10%) dependent on the pre-operative ejection fraction. Our data were in contrast to other published reports on the more beneficial effects of transmyocardial laser revascularization and should lead to further investigation of this experimental method. Transmyocardial laser revascularization should only be performed after failure of maximal anti-anginal therapy, and should be avoided when the left ventricular ejection fraction is < 40%.

Analysis of gene expression patterns in small amounts of human ventricular myocardium by a multiplex RNase protection assay

End-stage human heart failure is associated with changes in expression of steady-state messenger RNA (mRNA) levels. These changes correspond to alterations in protein levels and myocardial function and may have clinical implications regarding etiology, clinical state, or prognosis. However, analysis of mRNA levels in endomyocardial biopsies can be accomplished only by the quantitative polymerase chain reaction, which is difficult to standardize. The aim of the study was to evaluate whether the RNase protection assay is applicable to measure mRNAs of multiple genes simultaneously in small amounts of ventricular myocardium comparable to myocardial biopsies. Total RNA was prepared from left ventricular myocardium from terminally failing hearts with idiopathic (n=9) or ischemic cardiomyopathy (n=7) and from nonfailing control hearts (n=10). mRNA was measured by an optimized RNase protection assay for the beta1-adrenoceptor, the stimulatory G protein alpha-subunit (Gsalpha), phospholamban, the calcium ATPase of the sarcoplasmic reticulum (SERCA), beta-myosin heavy chain (beta-MHC), and the atrial natriuretic peptide (ANP). We extracted 10.7+/-2.1 microg total RNA from three myocardial biopsies taken in vitro. All of the six genes were measurable in duplicate in a total of 7 microg RNA. mRNAs of beta1-adrenoceptor, phospholamban, and SERCA were lower in failing than in nonfailing myocardium by 50%, 33%, and 42% respectively, whereas beta-MHC and Gsalpha mRNAs were unchanged. mRNA of ANP was expressed at high levels only in the failing myocardium, providing a highly specific and sensitive marker for discriminating nonfailing and failing hearts. A direct comparison with ANP and Gsalpha levels obtained by Northern blot analysis with 7.5 microg total RNA showed a good correlation between the two methods. The RNase protection assay is thus a suitable method for simultaneous measurements of multiple mRNA levels in human myocardial biopsies. Changes in mRNA levels closely reflected those identified by other methods using larger amounts of RNA. Increased myocardial ANP mRNA levels determined by the RNase protection assay may serve as a molecular marker of heart failure.

Acute pulmonary embolism: value of transthoracic and transesophageal echocardiography in comparison with helical CT

OBJECTIVE

The goal of this study was to prospectively compare the accuracy of transthoracic and transesophageal B-mode and Doppler echocardiography with helical CT for detecting acute pulmonary embolism.

SUBJECTS AND METHODS

Thirty-five consecutive patients underwent transthoracic and transesophageal echocardiography and contrast-enhanced helical CT. Echocardiographic examinations were analyzed for indirect criteria, including increased main pulmonary artery diameter, tricuspid regurgitation, and dilatation of the right ventricular cavity, as well as for direct thrombus visualization. Sensitivity, specificity, and negative and positive predictive values were calculated.

RESULTS

Pulmonary embolism was revealed by helical CT in 22 of 35 patients; in 11 of these 22 cases, central pulmonary embolism was seen. Transthoracic and transesophageal B-mode echocardiography failed to reveal pulmonary embolism in nine patients, two of whom had central pulmonary embolism. The sensitivity and specificity of the combination of both echocardiographic investigations were 59% and 77% respectively (82% and 92% for central pulmonary embolism). In three patients, pulmonary embolism was diagnosed by direct clot detection with transesophageal echocardiography. In two patients, only the indirect parameters indicated pulmonary embolism. Overall indirect echocardiographic parameters were characterized by a low sensitivity that ranged from 50% for tricuspid regurgitation to 21% for main pulmonary artery diameter.

CONCLUSION

In comparison with helical CT, transthoracic and transesophageal echocardiography had limited accuracy for detecting pulmonary embolism.

Positron emission tomography detects metabolic viability in myocardium with persistent 24-hour single-photon emission computed tomography 201Tl defects

BACKGROUND

Four-hour 201Tl redistribution images underestimate myocardial viability in patients with coronary artery disease (CAD). Because 4-hour defects often redistribute late, delayed imaging may enhance assessment of tissue viability. Myocardial metabolic activity was therefore assessed with positron emission tomography (PET) in 26 CAD patients with impaired ventricular function (ejection fraction, 32.1 +/- 13.9%) and 24-hour single-photon emission computed tomography (SPECT) 201Tl defects.

METHODS AND RESULTS

On circumferential profile analysis, PET ischemia was defined by preserved glucose metabolism in hypoperfused myocardium, and PET infarction was defined by concordant reductions in perfusion and metabolism. On 19 stress-redistribution and seven rest-redistribution SPECT studies, four observers visually scored 201Tl activity in eight segments on a scale from 0 (normal) to 3 (complete defect). Using an improvement in visual score > or = 0.75 to define redistribution, there were 100 fixed, 17 partially reversible, and 12 completely reversible defects. PET identified tissue metabolic activity in 51 (51%) segments with fixed defects (21 PET ischemia, 30 PET normal) and nine (53%) segments with partially reversible defects (five PET ischemia, four PET normal). When grouped by 24-hour score, the proportion of fixed defects with metabolic activity varied from 84% (scores < or = 1.4) to 15% (scores > 2.6). For partially reversible defects, only 53% with scores < 2.0 and one of two with scores > or = 2.0 were considered metabolically viable on PET. Of 12 completely reversible defects, six (50%) were normal, five (42%) had PET ischemia, and one (8%) had PET infarction. The proportion of fixed defects with metabolic activity did not depend on whether a rest or stress study was performed or on the change in visual score used to define 201Tl redistribution (0.25, 0.50, 0.75, and 1.00).

CONCLUSIONS

In CAD patients, PET identifies glucose metabolic activity in the majority of fixed 24-hour 201Tl defects. However, very severe (near-complete) 24-hour 201Tl defects are less likely to exhibit metabolic activity on PET imaging than are defects with less-pronounced reductions in segmental 201Tl activity.

Detection of coronary artery disease with positron emission tomography and rubidium 82

Myocardial blood flow was evaluated in 31 subjects with not only visual but also, for the first time, circumferential profile analysis of rubidium 82 (82Rb) images acquired with positron emission tomography. Fifteen were control subjects and 16 subjects had significant coronary artery disease, defined as 50% or greater diameter stenosis in a major coronary artery or a first-order branch. Simultaneous 82Rb images at three myocardial levels were obtained before and after intravenous dipyridamole plus handgrip stress. In patients with significant coronary artery disease, visual analysis correctly identified significant disease in 26 (76%) of 34 arteries and its absence in 12 (86%) of 14 normal arteries. According to circumferential profile analysis, these numbers were 91% and 86%, respectively. Thus circumferential analysis of 82Rb images, obtained before and after intravenous dipyridamole plus handgrip stress, yielded improved sensitivity and comparable specificity compared with visual analysis.

Development of N-butyl-N-(hydroxybutyl)-nitrosamine-induced tumors in the partially resected, proliferating rat urinary bladder in dependence upon the time of onset of stimulated DNA synthesis

Tumor development was investigated in the partially resected, proliferating urinary bladder of rats in dependence upon the onset of stimulated de novo DNA synthesis related to carcinogen dosing. N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) was used as carcinogen and administered by gavage in three fractionated doses (100 mg/kg body weight each) either during the phase of the most pronounced proliferation of the urothelium 30, 45 and 70 h after one-third resection of the bladder or 24 h and 1 week prior to partial cystectomy. When BBN was given during most increased DNA synthesis subsequent to one-third resection, the incidence of bladder tumors was reduced to 8.7% compared with 19.6% found in control animals with a non-resected, quiescent bladder. Tumor formation was neither inhibited nor enhanced when BBN was initially administered, followed by partial cystectomy 24 h or 1 week after the last carcinogen dose, yielding tumor incidences of 18.2% and 22.5%, respectively. Thus, the feeding of BBN during the period of maximum DNA synthesis inhibited tumor development in the partially resected bladder, while stimulation of cell replication subsequent to carcinogen administration did not influence the carcinogenic process initiated. The results obtained indicate that time of onset of stimulated DNA synthesis related to carcinogen dosing is the decisive factor in modifying urothelial carcinogenesis in the proliferating urinary bladder.

Emery-Dreifuss muscular dystrophy: disease spectrum and differential diagnosis

We report six patients with Emery-Dreifuss muscular dystrophy (EDMD) and four patients including one female with EDMD phenotype (EDMDP). This series includes one sporadic case who had previously been reported in this journal under the diagnosis of "rigid spine syndrome" in 1977. Time of observation ranged from three to ten years. Detailed cardiological assessment was performed in all patients, skeletal muscle biopsies were obtained from 9 out of 10 and cardiac muscle biopsies from 2 out of 10 patients. One patient showed evidence of cardiomyopathy in the absence of clinically apparent neuromuscular disease and one sibling of another EDMD patient reportedly had a similar combination of symptoms which, to our knowledge, has not yet been reported. Cardiac involvement was found to consist of four independent, albeit often combined features: 1) impairment of impulse generating cells; 2) conduction defects with atrial preponderance; 3) increased atrial and ventricular heterotopia; and 4) functional impairment of ventricular myocardium. Ventricular involvement as apparent from ventricular heterotopia, abnormal enddiastolic diameter, decrease of contractility and/or morphological evidence of ventricular myocardial disease was found in 7 out of 10 patients and confirmed by myocardial histopathology in two EDMD patients. In one myocardial biopsy extensive accumulations of intermediate filaments were observed, a rare finding, which has not been linked to EDMD before. Skeletal muscle biopsies showed evidence of myopathy throughout but several equivocal features such as fibre type grouping in EDMD and fibre type disproportion in EDMDP were also observed. The variability of clinical manifestation of both cardiac and neuromuscular disease encompassed a broader spectrum than apparent from the literature. The consequences for the inherent differential diagnosis are discussed.

[Comparison of the acute hemodynamic effect of nisoldipine (Bay k 5552) and nifedipine in patients with ischemia-induced left ventricular impaired function]

Calcium channel blockers of the dihydropyridine type have different sites of action that may cause negative inotropic effects in some patients; therefore, their use as systemic vasodilators in left heart failure may be limited. In 10 patients with coronary heart disease we compared the acute peripheral and central hemodynamic effects of i.v. nisoldipine vs. i.v. nifedipine intraindividually, using a sequential crossover protocol. All patients were subjected to right heart catheterization, arterial pressure monitoring, and simultaneous radionuclide angiography. The infusion of either calcium channel blocker was titrated to a similar steady-state reduction of mean arterial pressure by 15 +/- 3% and 15 +/- 2%, respectively, which reduced systemic vascular resistance by 25 +/- 5% and 17 +/- 2%, respectively. The required equally effective dosage was 0.17 +/- 0.06 micrograms/min/kg for nisoldipine and 0.58 +/- 0.1 micrograms/min/kg for nifedipine. In contrast to nifedipine, the administration of nisoldipine was associated with an increase in cardiac index by 0.45 +/- 0.33 l/min/m2 (p less than 0.05), stroke volume index by 3.91 +/- 3.0 ml/m2 (p less than 0.05), and left ventricular ejection fraction by 4.6 +/- 2.8% (p less than 0.05). Mean pulmonary capillary wedge pressure decreased with nisoldipine from 11.8 +/- 3.4 to 8.0 +/- 3.4 mm Hg (p less than 0.005) and mean pulmonary artery pressure decreased from 20.4 +/- 4.06 to 16.1 +/- 3.2 mm Hg (p less than 0.005), but was unaffected by nifedipine. Left and right ventricular endsystolic and enddiastolic volumes were not significantly altered by either drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of PET-acquired input functions for cardiac studies

To validate the determination of the arterial input function by noninvasive dynamic PET imaging, measurements of blood-pool activity in canine LV by PET were compared to beta probe measurements of arterial blood withdrawn directly from the LV. PET scans were done during intravenous bolus injections of [13N]ammonia or 82Rb, while the activity of blood withdrawn continuously from a catheter inserted in the LV was measured with a beta probe. PET determinations of LV blood-pool activity were compared with dispersion-corrected beta probe time-activity curves. In 15 experiments involving four dogs under a wide range of physiologic conditions, LV time-activity curves obtained with PET matched well in shape with those obtained with the beta probe. Linear regression yielded slopes within 10% of unity (95% confidence interval) and high correlation (r greater than 0.968, p less than 0.001). We conclude that noninvasive measurement of the arterial input function by dynamic PET imaging is valid.

[Right atrial thrombus formation following transvenous catheter ablation of the AV conduction system]

A case is reported in which the formation of a right atrial mass was detected by two-dimensional echocardiography 3 weeks after successful transvenous electrical ablation of the atrioventricular junction had been performed. The mass was attached to the atrial septum at the site where the electrode catheter used for the ablation had been located and it exhibited no mobility. It was interpreted as a right atrial thrombus induced by the ablation procedure. Although no pulmonary embolic events have been observed during a 7-month follow-up period, right atrial thrombus formation must be considered as a potentially dangerous complication of transvenous catheter ablation to control supraventricular arrhythmias.

Influence of ribose, adenosine, and "AICAR" on the rate of myocardial adenosine triphosphate synthesis during reperfusion after coronary artery occlusion in the dog

Recovery of adenosine triphosphate after myocardial ischemia is limited by the slow adenine nucleotide de novo synthesis and the availability of precursors of the nucleotide salvage pathways. We determined the adenine nucleotide de novo synthesis in the dog by infusion of [14C]glycine and the acceleration of adenine nucleotide built up by intracoronary infusion of ribose together with [14C]glycine or radiolabeled 5-amino-4-imidazolcarboxamide riboside or adenosine in the same animal model and with the same dosage of substrates (9 mmol) in postischemic and nonischemic myocardial tissue. After 45 minutes of occlusion of a side branch of the left coronary artery, the ischemic area was reperfused for 3 hours, and needle biopsies were taken for biochemical analysis. Adenine nucleotide de novo synthesis was found to be very slow (1.5 nmol/g wet weight per hour). The rate was doubled after ischemia. Adenine nucleotide synthesis was accelerated 5-fold by ribose, the basic substrate of the adenine nucleotide de novo synthesis, 9-fold by 5-amino-4-imidazolcarboxamide riboside, an intermediate of the adenine nucleotide de novo synthesis and 90-fold by adenosine, a substrate of the nucleotide salvage pathway. Therefore, only adenosine infusion resulted in a measurable increase of adenosine triphosphate levels after 3 hours of reperfusion, but over a longer time period, ribose or 5-amino-4-imidazol-carboxamide riboside also can be expected to replenish reduced myocardial adenosine triphosphate faster than adenine nucleotide de novo synthesis. Studies with radiolabeled 5-amino-4-imidazol-carboxamide riboside showed significant incorporation of radioactivity into 5-amino-4-imidazol-carboxamide ribose triphosphate which had also risen measurably during 5-amino-4-imidazol-carboxamide ribose infusion, and which is not normally found in heart muscle.

Myocardial protection by collateral vessels during experimental coronary ligation: a prospective study in a canine two-infarction model

Previous work of this laboratory has shown that collateral flow can be increased over six weeks by a subcritical external constriction of the circumflex artery causing a 50 +/- 10% reduction of postocclusive reactive hyperemia. To investigate collateral function in acute myocardial infarction, the model was used to ligate two distant coronary branches on the ventricle simultaneously in order to compare in 8 dogs infarct size and perfusion area of the ligated vessels in control and collateralized sections. The acute collateral flow measured 7.2 +/- 2.5 ml/100 g/min-1 and increased to 17.3 +/- 6.7 (p less than 0.001) over 6 weeks. Separate analysis revealed a predominant increase of collateral flow in the epicardial layers 23.1 +/- 7.5 (p less than 0.01) versus 6.9 +/- 2.8 (p less than 0.01) in the subendocardium. Infarct size in the control area was 52.0 +/- 14.7% of the perfusion area, in the collateralized zone 19.0 +/- 14.2% (p less than 0.001). Infarct size expressed as per cent of perfusion area and collateral flow in the area at risk expressed as per cent of flow of normal sections correlated: (r = 0.76; p less than 0.05). Therefore, infarct size after a 6 hour coronary occlusion can be considered a function of the collateral flow over normal perfusion ratio. Localized induction of collaterals in this model caused a significant reduction of infarct size in relation to the perfusion area at risk.

The relationship between the perfusion deficit, infarct size and time after experimental coronary artery occlusion

It is well known that coronary occlusions of short duration do not produce infarcts in the dog heart, but permanent occlusions always do. The aim of this paper was to investigate with quantitative direct measurements the determinants of infarct size within these two extremes. We measured left ventricular MV2, coronary and collateral blood flow and infarct size after occlusion times varying between 45 minutes and 24 hours. MVO2 was kept low in one group by establishing low heart rates with a synthetic opiate. In another group, MV2 was kept elevated by giving synthetic catecholamines (dobutamine) that stimulated contractility and heart rate. Under the described experimental conditions LV-coronary blood flow reflected the true demand for blood and oxygen. The ratio of collateral blood flow over coronary blood flow (both measured with tracer microspheres) was therefore a good approximation of the supply-demand ratio (SD). Since collateral flow was inhomogeneously distributed across the left ventricular wall, the SD-ratio showed similar variations. As the collateral blood flow increased with elapsed time after coronary occlusion, the SD-ratio improved. Since high LV-O2-demand increased coronary flow but exerted practically no influence on collateral flow, this situation influenced the SD-ratio in a negative way. Decreased O2-demand had the opposite effect. The SD-ratio is thus a valid expression of the relative and absolute blood flow deficit as influenced by the local and general O2-demand. We found significant and characteristic correlations between the SD-ratio and infarct which was only influenced by time. A blood flow deficit of 90% (i.e., collateral flow = 10% of required flow) produced a 50%-infarct (relative to the risk-region) with a 45-min occlusion but a 90%-infarct with occlusion times of 3 hrs and longer. If the perfusion deficit is only 0.5 (collateral flow = 50% of required flow), no infarct is detectable at occlusion times shorter than 3 hrs. Small perfusion deficits of only 20% below required flow caused infarctions at 24 hrs and longer. In the group where the SD-ratio was closer to unity because of a low overall LV-O2-consumption (bradycardia), infarcts at t = 24 hrs were significantly smaller than in the group with a high LV-MVO2.

Development of collaterals. Application of external subcritical fixed constrictors in a canine model

A canine model for a standardized induction of collaterals is presented with a fixed external constrictor that is not designed to induce an occlusion of the coronary artery and at least over the timespan of 6 weeks does not impair perfusion under resting conditions in the myocardium-at-risk. The coronary constriction was standardized by a reduction of the postocclusive reactive hyperemia of 50%. Flow measurements were performed by flowmeter and by radioactive microspheres acutely and after an interval of 6 weeks of constriction. The results showed an increase of the collateral flow from 21.2 +/- 11.8 ml/100 g/min-1 to 42.8 +/- 16.2 ml/100 g/min-1 (p less than 0.05). The regional perfusion exhibited a transmyocardial gradient in favour of the subepicardial layers with 49.3 +/- 25 ml/100 g/min-1 as compared to 33.1 +/- 17.3 ml/100 g/min-1 (p less than 0.05) of the endocardial layers. Reactive hyperemia, as determined by flowmeter, was decreased by 21% after 6 weeks on account of slow progression of the coronary constriction due to intimal reactions, whereas reactive hyperemia, as determined by the microsphere method, increased by 9% due to additional collateral channels.

Loss of canine myocardial nicotinamide adenine dinucleotides determines the transition from reversible to irreversible ischemic damage of myocardial cells

We investigated if the loss of nicotinamide coenzymes in ischemic-infarcted myocardium may be responsible for the transition from reversibly ischemic to irreversibly infarcted cell damage. The LAD was occluded in 6 dogs for 4 h. Transmural needle biopsies were taken from he ischemic-infarcted region after 1/2, 1, 11/2, 2, and 4 h of ischemia and further divided into subepicardial and subendocardial halves. At each time interval the concentration of the nicotinamide coenzymes NAD, NADH, and NADPH were measured, and the degree of cellular injury was evaluated by electron microscopy. The glycohydrolase activity (EC 3.2.2.5), the enzyme which splits NAD, was determined in brain, myocardium, kidney, and skeletal muscle of 4 rats. Total NAD, the sum of NAD and NADH, started to decrease significantly in the ischemic subendocardium 1 h after onset of ischemia. Degradation of NADPH occurred later. Loss ot total NAD was about 60-70% when electron microscopy diagnosed irreversible cell injury. The glycohydrolase activity was the highest in brain followed by myocardium, kidney, and skeletal muscle, reflecting the different tolerances of these tissues towards ischemia. The key mechanism for ischemic injury seems to be the tissue acidosis which activates the glycohydrolase leading to a loss of the vital coenzymes.