Prognostic assessment of stable coronary artery disease as determined by coronary computed tomography angiography: a Danish multicentre cohort study

Aims

To examine the 3.5 year prognosis of stable coronary artery disease (CAD) as assessed by coronary computed tomography angiography (CCTA) in real-world clinical practice, overall and within subgroups of patients according to age, sex, and comorbidity.

Methods and results

This cohort study included 16,949 patients (median age 57 years; 57% women) with new-onset symptoms suggestive of CAD, who underwent CCTA between January 2008 and December 2012. The endpoint was a composite of late coronary revascularization procedure >90 days after CCTA, myocardial infarction, and all-cause death. The Kaplan-Meier estimator was used to compute 91 day to 3.5 year risk according to the CAD severity. Comparisons between patients with and without CAD were based on Cox-regression adjusted for age, sex, comorbidity, cardiovascular risk factors, concomitant cardiac medications, and post-CCTA treatment within 90 days. The composite endpoint occurred in 486 patients. Risk of the composite endpoint was 1.5% for patients without CAD, 6.8% for obstructive CAD, and 15% for three-vessel/left main disease. Compared with patients without CAD, higher relative risk of the composite endpoint was observed for non-obstructive CAD [hazard ratio (HR): 1.28; 95% confidence interval (CI): 1.01-1.63], obstructive one-vessel CAD (HR: 1.83; 95% CI: 1.37-2.44), two-vessel CAD (HR: 2.97; 95% CI: 2.09-4.22), and three-vessel/left main CAD (HR: 4.41; 95% CI :2.90-6.69). The results were consistent in strata of age, sex, and comorbidity.

Conclusion

Coronary artery disease determined by CCTA in real-world practice predicts the 3.5 year composite risk of late revascularization, myocardial infarction, and all-cause death across different groups of age, sex, or comorbidity burden.

The Western Denmark Cardiac Computed Tomography Registry: a review and validation study

BACKGROUND

As a subregistry to the Western Denmark Heart Registry (WDHR), the Western Denmark Cardiac Computed Tomography Registry (WDHR-CCTR) is a clinical database established in 2008 to monitor and improve the quality of cardiac computed tomography (CT) in Western Denmark.

OBJECTIVE

We examined the content, data quality, and research potential of the WDHR-CCTR.

METHODS

We retrieved 2008-2012 data to examine the 1) content; 2) completeness of procedure registration using the Danish National Patient Registry as reference; 3) completeness of variable registration comparing observed vs expected numbers; and 4) positive predictive values as well as negative predictive values of 19 main patient and procedure variables.

RESULTS

By December 31, 2012, almost 22,000 cardiac CTs with up to 40 variables for each procedure have been registered. Of these, 87% were coronary CT angiography performed in patients with symptoms indicative of coronary artery disease. Compared with the Danish National Patient Registry, the overall procedure completeness was 72%. However, an additional medical record review of 282 patients registered in the Danish National Patient Registry, but not in the WDHR-CCTR, showed that coronary CT angiographies accounted for only 23% of all nonregistered cardiac CTs, indicating >90% completeness of coronary CT angiographies in the WDHR-CCTR. The completeness of individual variables varied substantially (range: 0%-100%), but was >85% for more than 70% of all variables. Using medical record review of 250 randomly selected patients as reference standard, the positive predictive value for the 19 variables ranged from 89% to 100% (overall 97%), whereas the negative predictive value ranged from 97% to 100% (overall 99%). Stratification by center status showed consistently high positive and negative predictive values for both university (96%/99%) and nonuniversity centers (97%/99%).

CONCLUSION

WDHR-CCTR provides ongoing prospective registration of all cardiac CTs performed in Western Denmark since 2008. Overall, the registry data have a high degree of completeness and validity, making it a valuable tool for clinical epidemiological research.

Impact of luminal density on plaque classification by CT coronary angiography

Non-invasive coronary CT angiography (CCTA) has the potential to characterize the composition of non-calcified coronary plaques. CT-density values characterized by Hounsfield Units (HU) may classify non-calcified plaques as fibrous or lipid-rich, but the luminal density caused by the applied contrast material influences HU in the plaques in vitro. The influence of luminal density on HU in non-calcified plaques in vivo is unknown. Hence the purpose of this study was to test whether plaque characterization by CCTA in vivo depends on luminal density. Two CCTA-scans using two different contrast protocols were obtained from 14 male patients with coronary artery disease. The two contrast protocols applied resulted in high and low luminal density. Eleven non- calcified and 13 calcified plaques were identified and confirmed by intravascular ultrasound. Luminal attenuation differed with the two contrast protocols; 326[284;367] vs. 118[103;134] HU (P < 0.00001). In non-calcified plaques mean HU-values was lower 48[28;69] vs. 11[-4;25] HU (P = 0.004) with the low density protocol. As a consequence three out of eleven non-calcified plaques (27%) were reclassified from fibrous (high) to lipid rich (low). For calcified plaques a less pronounced but still significant difference in HU-values was found with the low luminal density. 770[622;919] vs. 675[496;855] HU (P = 0.02).

CONCLUSION

Non-calcified plaques can be identified and classified by CCTA. However, the luminal density affects the absolute HU of both non-calcified and calcified plaques. Characterization and classification of non-calcified plaques by absolute CT values therefore requires standardization of contrast protocols.

Increased mortality after dronedarone therapy for severe heart failure

BACKGROUND

Dronedarone is a novel antiarrhythmic drug with electrophysiological properties that are similar to those of amiodarone, but it does not contain iodine and thus does not cause iodine-related adverse reactions. Therefore, it may be of value in the treatment of patients with heart failure.

METHODS

In a multicenter study with a double-blind design, we planned to randomly assign 1000 patients who were hospitalized with symptomatic heart failure and severe left ventricular systolic dysfunction to receive 400 mg of dronedarone twice a day or placebo. The primary end point was the composite of death from any cause or hospitalization for heart failure.

RESULTS

After inclusion of 627 patients (310 in the dronedarone group and 317 in the placebo group), the trial was prematurely terminated for safety reasons, at the recommendation of the data and safety monitoring board, in accordance with the board's predefined rules for termination of the study. During a median follow-up of 2 months, 25 patients in the dronedarone group (8.1%) and 12 patients in the placebo group (3.8%) died (hazard ratio in the dronedarone group, 2.13; 95% confidence interval [CI], 1.07 to 4.25; P=0.03). The excess mortality was predominantly related to worsening of heart failure--10 deaths in the dronedarone group and 2 in the placebo group. The primary end point did not differ significantly between the two groups; there were 53 events in the dronedarone group (17.1%) and 40 events in the placebo group (12.6%) (hazard ratio, 1.38; 95% CI, 0.92 to 2.09; P=0.12). More increases in the creatinine concentration were reported as serious adverse events in the dronedarone group than in the placebo group.

CONCLUSIONS

In patients with severe heart failure and left ventricular systolic dysfunction, treatment with dronedarone was associated with increased early mortality related to the worsening of heart failure. (ClinicalTrials.gov number, NCT00543699.)

Effects of losartan and captopril on left ventricular systolic and diastolic function after acute myocardial infarction: results of the Optimal Trial in Myocardial Infarction with Angiotensin II Antagonist Losartan (OPTIMAAL) echocardiographic substudy

BACKGROUND

Angiotensin-converting enzyme inhibitors have been shown to attenuate adverse remodeling after acute myocardial infarction (AMI), and the same has been suggested for angiotensin II type 1 receptor antagonists in animal models. Therefore the aim of the study was to compare the effects of losartan and captopril on regional systolic, diastolic, and overall left ventricular (LV) function after AMI.

METHODS

Two hundred twenty-five patients aged > or =50 years with documented AMI and heart failure and/or LV dysfunction were randomly assigned treatment with either losartan (50 mg/d) or captopril (50 mg 3 times/d). Echocardiography was performed at randomization and after 3 months; echocardiograms were analyzed blinded at the core laboratory. Main outcome measures were changes in wall motion score index (WMSI), E-wave deceleration time (E-DT), and Tei index of overall LV function.

RESULTS

WMSI decreased in both groups (losartan 1.58 +/- 0.23 to 1.52 +/- 0.26, P =.009, captopril 1.60 +/- 0.24 to 1.48 +/- 0.22, P <.001), although the decrease was greater in patients allocated to captopril (captopril -0.12 +/- 0.17 vs losartan -0.05 +/- 0.19, P =.007). In both groups E-DT increased, although the increase was significant only in patients treated with captoril (193 +/- 61 ms to 208 +/- 70 ms, P =.05). The change in E-DT was not different between treatment groups (captopril 14 +/- 74 ms vs losartan 7 +/- 80 ms, P =.52). Tei index decreased in both groups (losartan 0.59 +/- 0.13 to 0.55 +/- 0.15, P =.04, captopril 0.62 +/- 0.15 to 0.55 +/- 0.13, P <.001). However, the reduction was significantly greater in patients treated with captopril (captopril -0.08 +/- 0.14 vs losartan -0.03 +/- 0.14, P =.01).

CONCLUSION

Losartan and captopril improve systolic and overall LV function after AMI, but the benefit is greater for patients treated with captopril.

Carvedilol does not alter the insulin sensitivity in patients with congestive heart failure

BACKGROUND

Congestive heart failure (CHF) has previously been shown to be associated with insulin resistance and hyperinsulinemia. A beneficial effect of the non-selective beta-blocker carvedilol has been demonstrated in patients with CHF. However, whether the drug affects the insulin sensitivity (S(i)) is unknown.

AIMS

To investigate whether treatment with carvedilol alters the S(i) in patients with CHF during a prospective, double-blinded, placebo-controlled study.

METHODS AND RESULTS

The patients were randomized to receive either carvedilol (n=29) or matched placebo (n=17). Insulin and glucose responses were measured during a 0.3 g/kg intravenous glucose tolerance test, and S(i) was calculated according to Bergman's Minimal Model. Baseline S(i) values correlated significantly with body mass index (r=-0.42, P=0.002), plasma urate (r=-0.42, P=0.002), plasma HDL-cholesterol (r=0.39, P=0.003), maximal oxygen uptake (r=0.35, P=0.009), plasma triglycerides (r=-0.34, P=0.01) and weight (r=-0.29, P=0.03). During the study the insulin sensitivity was unchanged in the carvedilol group compared with placebo (2.63+/-1.45 to 2.38+/-1.64 vs. 2.81+/-2.36 to 2.48+/-1.84x10(-4) min(-1)/mUl(-1), P=0.83).

CONCLUSION

Additional treatment with carvedilol is neutral with regard to influence the insulin sensitivity in patients with mild to moderate CHF.

Effect of carvedilol on microcirculatory and glucose metabolic regulation in patients with congestive heart failure secondary to ischemic cardiomyopathy

In a randomized (2:1), double-blinded design study, we studied 25 patients with congestive heart failure (66 +/- 9 years, ejection fraction 30 +/- 7%) before and after 23-week treatment with the beta blocker carvedilol 25 mg twice daily (n = 17) or placebo (n = 8) in addition to standard therapy. Using dynamic positron emission tomography, myocardial perfusion at rest and perfusion reserve after dipyridamole (0.56 mg/kg/min) were measured. Myocardial glucose uptake and plasma levels of catecholamines were also estimated. Carvedilol treatment reduced the rate-pressure product (8,781 +/- 2,672 vs 6,342 +/- 1,346, p <0.01) and improved ejection fraction (29 +/- 7% vs 37 +/- 11%, p <0.001), whereas no changes were observed in the control group. Perfusion at rest was unchanged in the placebo group (0.81 +/- 0.17 vs 0.86 +/- 0.23 ml/g/min, p = NS), whereas the carvedilol-treated group showed a significant reduction (0.88 +/- 0.26 vs 0.75 +/- 0.16 ml/g/min, p <0.05). Dipyridamole-induced hyperemia was significantly reduced after carvedilol treatment (1.51 +/- 0.45 vs 1.31 +/- 0.51 ml/g/min, p <0.001), whereas myocardial perfusion reserve was unaltered. Carvedilol did not alter myocardial glucose uptake (0.33 +/- 0.14 vs 0.32 +/- 0.12 micromol/g/min, p = NS) or the plasma catecholamines levels. We therefore conclude that in patients with congestive heart failure, carvedilol reduced resting and hyperemic perfusion. No effect on glucose uptake or catecholamine levels was observed. The reduced perfusion at rest must reflect reduced perfusion demand and thereby a higher threshold for myocardial ischemia and protection against myocardial damage or malignant arrhythmia. These effects may serve as a pathophysiologic explanation for the reduced mortality in patients with congestive heart failure who receive carvedilol.

Time course of myocardial viability after acute myocardial infarction: an echocardiographic study

The recognition of dysfunctional but viable myocardium after acute myocardial infarction (MI) may be of importance for both patient prognostication and the decision for revascularization. Low-dose dobutamine echocardiography (LDDE) has been shown to be a reliable technique in detecting reversibility of dysfunctional myocardium. The aim of the present study was to assess by LDDE possible time-dependent changes in myocardial viability and to evaluate the value of LDDE used in the postinfarction period. Twenty-seven patients with acute MI underwent LDDE on day 6, 30, and 90. At LDDE day 6, 41% of the affected segments showed a positive response to LDDE. At later examination on day 30 and 90, only 32% and 18%, respectively, of the dysfunctioning segments responded to dobutamine stimulation, with a significant decline in response (p < 0.0001), indicating loss of viability. Spontaneous segmental outcome was significantly better for LDDE-responding segments than for nonresponding segments (p = 0.0001). This study indicated that myocardial viability may be temporary and that a time-dependent loss of viability may take place during the first months after MI.

Evaluation and prognostic significance of left ventricular diastolic function assessed by Doppler echocardiography in the early phase of a first acute myocardial infarction

AIM

To study the prognostic significance of left ventricular diastolic function evaluated by transmitral and pulmonary venous flow velocities obtained in the early phase of a first acute myocardial infarction in relation to later development of congestive heart failure.

METHODS

Pulsed Doppler echocardiography of transmitral and pulmonary venous flow was assessed in 65 consecutive patients with a first myocardial infarction within 1 h of arrival in the coronary care unit.

RESULTS

A univariate regression analysis identified age, left ventricular ejection fraction < or = 45%, mitral E deceleration time < or = 130 ms, E/A ratio > 1.5, peak pulmonary venous atrial flow velocity > or = 30 cm.s-1 and a difference between mitral and pulmonary venous atrial flow duration < 0 ms as variables significantly related to the development of congestive heart failure. However, in a multivariate analysis only mitral E deceleration time < or = 130 ms and age were significant independent variables related to the development of congestive heart failure during the first week following a first acute myocardial infarction.

CONCLUSION

Assessment of left ventricular diastolic function complements measurements of systolic function in the evaluation of cardiac function, and mitral deceleration < or = 130 ms best identifies patients at risk of development of congestive heart failure following acute myocardial infarction.

Incipient cardiomyopathy in young insulin-dependent diabetic patients: a seven-year prospective Doppler echocardiographic study

Two echo-Doppler cardiographic investigations were performed 7 years apart in 17 insulin-dependent diabetic children without hypertension or nephropathy in order to detect early signs of cardiac abnormalities in this group without ischaemic heart disease. Relative to two matched control groups, the patients had reduced increase in left ventricular size (p < 0.01) and stroke volume (p < 0.05). An initially reduced end systolic wall stress and increased fractional shortening (p < 0.003) was normalized during the 7 years. Concomitant with early signs of autonomic neuropathy and aortic stiffening, left ventricular filling changed with increased velocity during atrial contraction (p < 0.01) correlating to the decreased stroke volumes (r = -0.57, p = 0.016). These early changes could suggest left ventricular restriction but could also reflect a changed sympathetic/parasympathetic balance in diabetic children. A reduced left ventricular cavity size and increased atrial ejection has thus been described in these insulin-dependent children without hypertension, nephropathy or evidence for ischaemic heart disease, suggesting the existence of a metabolically-induced cardiomyopathy.

[Left ventricular diastolic function assessment by transthoracic Doppler echocardiography]

Left ventricular diastolic dysfunction is currently recognized in patients with different heart diseases. Three abnormal filling patterns of the left ventricle detected by pulsed-Doppler echocardiography are observed in patients with heart disease. Each filling pattern is characterised by different symptoms, and by differences in function and dimension of the left atrium and filling pressures. Mitral and pulmonary venous flow velocities and durations obtained by pulsed Doppler technique can be used to evaluate left ventricular diastolic function in patients with different heart diseases. However, several factors affect the transmitral and pulmonary venous flow such as age, heart rate, positioning of the sample volume and aortic- and mitral valve insufficiency. These factors must be taken into consideration when the diastolic function is evaluated by pulsed Doppler technique.

Increased number of myocardial voltage-gated Ca2+ channels and unchanged total beta-receptor number in long-term streptozotocin-diabetic rats

In order to elucidate further the abnormal myocardial Ca2+ metabolism in diabetes mellitus, voltage-gated Ca2+ channels and beta-receptors were quantified in myocardial membranes of short- and long-term diabetic rats. Diabetes was induced by an injection of streptozotocin (STZ). Animals were killed 2, 4, 7, 90 and 200 days after STZ. A group of diabetic animals were treated with insulin for 20 days following 180 days of untreated diabetes. Diabetic animals developed low triiodothyronine syndrome. During short-term diabetes, the maximum binding capacity (MBC) for Ca2+ channels was reduced by 25% at day 4 (p < 0.05) and the beta-receptor MBC was reduced by 48% (p < 0.05). A normalizing tendency was observed at day 7 for both receptor types; insulin-treated rats did not differ from controls at that time. After 90 and 200 days of untreated diabetes the Ca2+ channel MBC had increased by 36% and 27%, respectively (p < 0.05). Twenty days of strictly regulated blood glucose following 180 days of untreated diabetes totally normalized the Ca2+ channel MBC. This is in contrast to a previous report where insulin treatment did not normalize the Ca2+ channel MBC. Total beta-receptor MBCs did not differ from control values 90 and 200 days after STZ. In conclusion, an increase in rat myocardial Ca2+ channel MBC during long-term diabetes was fully normalized by short-term insulin treatment. The increase in sarcolemmal Ca2+ channels could serve to compensate for a defect coupling of the beta-receptor to adenylate cyclase. An elevated Ca2+ channel number may, at least theoretically, lead to increased Ca2+ flow across the cardiac sarcolemma and in this way contribute to the diabetic cardiomyopathy by increasing the intracellular Ca2+ concentration.

Abnormal left ventricular diastolic function during cold pressor test in uncomplicated insulin-dependent diabetes mellitus

1. Insulin-dependent diabetes mellitus is a known risk factor for congestive heart failure and an early diastolic dysfunction has been described. In order to see if diabetes itself and not complications like hypertension, nephropathy or ischaemic heart disease can be considered responsible for the abnormal diastolic function of the left ventricle, 17 young patients with uncomplicated insulin-dependent diabetes mellitus and 12 control subjects were exposed to a cold pressor test. 2. Blinded echo-Doppler examination was performed before and during the test. During basal conditions, left ventricular dimensions and volumes were smaller in diabetes and atrial contributions to left ventricular filling were increased. 3. During the cold pressor test, isovolumic relaxation time increased, peak early filling velocity (E) decreased, E deceleration time decreased and atrial contribution (A) increased significantly in diabetes, while only A increased in the control group. A marked increase in left atrial ejection force was seen in diabetes only (P < 0.002). This difference was seen in spite of comparable reductions in mitral area and atrioventricular compliance in the two groups. 4. The hyperfunction of the left atrium in diabetes is hypothesized to be due to reduce size of the left ventricle combined with incipient autonomic neuropathy.

[Allergic myocarditis in clozapine treatment]

Clozapine is a high-dose neuroleptic, which is recommended only for those cases in which patients have failed to respond adequately to standard antipsychotic drugs. This report describes a 45 year old man with ischaemic heart disease who died of cardiogenic shock 11 days after starting treatment with clozapine. Autopsy showed apart from coronary atherosclerosis and interstitial fibrosis a considerable infiltration of eosinophilic granulocytes in the myocardium suggesting myocarditis as the cause of death.

Abnormal changes in transmitral flow after acute exposure to nitroglycerin and nifedipine in uncomplicated insulin-dependent diabetes mellitus: a Doppler echocardiographic study

To study the left ventricular (LV) diastolic function in uncomplicated insulin-dependent diabetic patients without hypertension (n = 25) and comparable controls (n = 15), the effect of acute administration of nitroglycerin and nifedipine on cavity dimensions and transmitral flow pattern was investigated by Doppler echocardiography. At baseline no significant differences in any of the LV Doppler echocardiographic parameters were seen in the two groups. Only in diabetics did nitroglycerin diminish LV diastolic and systolic diameter significantly (p < 0.0002 and 0.004, respectively), reducing the stroke volume from 70 +/- 16 to 64 +/- 20 ml, p < 0.01. The decrease in stroke volume correlated significantly to hemoglobin (Hb) A1c level (r = 0.42, p = 0.036). An excessive preload reducing effect on venous capacitance vessels is assumed in diabetes, and this preload reducing effect was also reflected in transmitral flow pattern where E-wave/A-wave ratio decreased significantly only in the diabetic subjects (p < 0.0005). Nifedipine induced the same degree of sympathetic activation in the two groups, but an increase in LV early peak filling rate (E wave) was seen in diabetes only (63.3 +/- 13.5 to 66.8 +/- 13.5 mm, p < 0.01). The atrial filling of LV (A wave) was increased significantly in both groups. Thus an abnormal LV diastolic function can be disclosed by these pharmacologic challenges. Regulation of preload and its influence on transmitral flow pattern in diabetes deserves further investigation, as does the influence of calcium antagonists on early relaxation in the diabetic myocardium.

Reduced left ventricular afterload and increased contractility in children with insulin-dependent diabetes mellitus: an M-mode and Doppler-echocardiographic evaluation of left ventricular diastolic and systolic function

Twenty-three children with diabetes mellitus, their ages ranging from 0.2-9.8 years, but with no sign of diabetic microvascular disease were investigated by M-mode and Doppler echocardiography, along with a comparable group of control subjects. In the diabetics, the fractional shortening and the mean velocity of fractional shortening were 14 and 18% higher, respectively, whereas the left ventricular end-systolic wall stress, an indicator of left ventricular afterload, was markedly reduced (22%). Assuming an unchanged preload in the two groups, this indicates a reduced afterload in these children. Systolic and diastolic time intervals, heart rate, and blood pressure were similar in diabetics and controls. Doppler-derived transmitral left ventricular filling indices were also similar. Thus, in these diabetic children no signs of left ventricular diastolic abnormality were detected. The state of hypercontractility of the left ventricle is considered to be due to a reduced afterload in early insulin-dependent diabetes.

[Atypical meningococcal disease diagnosed with meningococcal antibody test]

The case histories of three patients with atypical meningococcal disease in whom the diagnosis was established by means of a meningococcal antibody test (MAT) are presented. One patient had clinically atypical, but bacteriologically verified meningococcal disease; the other two patients were primarily suspected of having viral infections. The usefulness of investigation for meningococcal antibodies in serum from patients with assumed meningococcal disease or with fever of unknown origin is stressed.

Early changes in thyroid hormone metabolism in the heart, liver, and brown adipose tissue during the induction of low T3 syndrome in streptozotocin-diabetic rats

In order to elucidate the day-by-day development of low T3 syndrome, we made rats diabetic by an injection of streptozotocin. Untreated controls killed at day 0 and rats treated for 8 days with insulin after they had received streptozotocin served as controls. Sub-groups of animals were killed 1, 2, 3, 4 and 8 days after streptozotocin. In serum, heart and liver, T3 was depressed to less than 50% of controls at day 4, whereas the insulin-treated rats differed from controls only as to heart T3. Heart iodothyronine 5'-deiodinase activity was depressed to a minimum at day 3 and depression was not prevented by insulin. Liver iodothyronine 5'-deiodinase activity had not reached a minimum at day 8, and again, insulin treatment did not normalize this parameter. T3 contents and iodothyronine 5'-deiodinase activity in brown adipose tissue did not differ from values in controls at any point of time. Thus, in the rats with low T3 syndrome induced by streptozotocin-diabetes, a lowered iodothyronine 5'-deiodinase activity is not fully inhibited by insulin treatment, whereas the T3 content in the liver is re-established during an observation period of 8 days. A direct toxic effect of streptozotocin seems unlikely as an in vitro study showed no influence of streptozotocin on iodothyronine 5'-deiodinase activity in the liver. The study thus indicates that iodothyronine 5'-deiodinase activity in the heart and liver is depressed in experimental diabetes, despite near optimal regulation of blood glucose, and we suggest that lowered intracellular T3 production could, after some time, result in a hypothyroid state in different tissues.

Regression of glycogen nephrosis in experimental diabetes after pancreatic islet transplantation

Glycogen nephrosis, i.e. the Armanni-Ebstein lesion which manifests itself by intracellular accumulation of beta-glycogen has been studied in two groups of streptozotocin diabetic rats and compared to controls. One diabetic group was left untreated and the other diabetic group received pancreatic islet transplantation after 4 weeks duration of diabetes. The kidneys were studied after another 4 week period with normoglycemia. In the non-transplanted diabetic animals glycogen containing tubules comprised 43% of the distal tubule length in the cortex but in the transplanted animals no abnormal, glycogen containing cells could be recovered at the light microscope level. Measurements of the total distal tubule length in the non-transplanted diabetic animals showed that the distal tubules increased in length by 24%. In the transplanted diabetic animals distal tubule length remained the same as in the non-transplanted diabetic animals in spite of normalization of the tubular morphology. This finding could possibly be responsible for the incomplete normalization of kidney weight after treatment.

Myocardial cell dysfunction in diabetes mellitus. A review of clinical and experimental studies

Evidence for an abnormal myocardial cell function in diabetes mellitus, influenced by acute metabolic changes, has appeared within recent years. Few but interesting clinical studies focus on this aspect of diabetic cardiopathy, and experimental studies have delivered possible explanations at the cellular level. These are concerned with the intracellular calcium homeostasis and transsarcolemmal receptor signaling. Because these changes are reversible by short-term insulin treatment, a new aspect for the study of diabetic heart disease has appeared.

Abnormal myocardial calcium uptake in streptozocin-diabetic rats. Evidence for a direct insulin effect on catecholamine sensitivity

Myocardial calcium uptake after isoproterenol (ISO) in the isolated, perfused heart was investigated at 24-h intervals after the injection of streptozocin (STZ) in rats. After 4 days, when hyperglycemia had persisted for 3 days, myocardial calcium uptake in response to this strong beta-adrenergic agonist fell significantly to the level of unstimulated hearts, which also was the level of propranolol-pretreated hearts exposed to ISO. Insulin, when given in vivo 60-90 min before perfusion, led to a complete normalization of this ISO response in diabetic rats (duration 8 days), while in vitro addition of insulin to the perfusate (0.1 U/ml) significantly increased, while not completely normalizing, the ISO-induced myocardial calcium uptake. Insulin, therefore, has a direct effect on this beta-adrenergic response in diabetic rats and streptozocin in itself does not cause the desensitization. Considering the essential role of this calcium transport for the electromechanical coupling in the heart, such metabolically induced changes in catecholamine sensitivity might hypothetically have relevance for the increased incidence of heart failure in diabetes.

Myocardial calcium uptake in streptozotocin diabetic and control rats after dibutyryl-cAMP; alpha-adrenergic stimulation and calcium deprivation

Previous studies have shown a decreased myocardial calcium uptake after beta-adrenergic stimulation with isoproterenol in isolated perfused hearts from streptozotocin diabetic rats. Abnormalities in the beta-receptor-adenylate cyclase system could explain this but in order to circumvene the receptor we studied the effect of the permeable cAMP analogue, dibutyryl-cAMP on this calcium uptake. A marked increase was seen in control hearts while no increase could be registered in diabetic hearts. Defects in the protein kinase phosphorylation system or in the protein kinase substrate in the sarcolemma are suggested. alpha-Adrenergic stimulation with phenylephrine, being a cAMP independent positive inotropic agent, was also tested but no increase in calcium uptake was seen in either control or diabetic hearts. This could be due to a different effect on calcium currents during action potential after alpha-stimulation compared to the beta-adrenergic effect. Reexposure to calcium after calcium deprivation leads to excessive myocardial calcium uptake (calcium paradox), but the increase was significantly smaller in diabetic hearts, suggesting a differential responsiveness to the damage induced by this procedure. Early biochemical abnormalities in the basement membrane or in the composition and calcium binding ability of the sarcolemma could possibly constitute a common final site for the defect myocardial calcium uptake after isoproterenol, db-cAMP and calcium deprivation in streptozotocin diabetic rats.

Acute insulin treatment normalizes the resistance to the cardiotoxic effect of isoproterenol in streptozotocin diabetic rats. A morphometric study of isoproterenol induced myocardial fibrosis

The acute effect of insulin treatment on the earlier reported protective effect of streptozotocin diabetes against the cardiotoxic effect of high doses of isoproterenol (ISO) was investigated in rats. Thirty to 135 min after the injection of crystalline insulin, ISO was given subcutaneously and when ISO induced fibrosis in the myocardium was morphometrically analyzed 7 days later, a highly significant correlation (r = 0.83, 2 p = 0.006) to the slope of the fall in blood glucose after insulin treatment appeared. The myocardial content of catecholamines was estimated in these 8 day diabetic rats. The norepinephrine content was significantly increased while epinephrine remained unchanged. An enhanced sympathetic nervous system activity with a consequent down regulation of the myocardial beta-adrenergic receptors could, therefore, explain this catecholamine resistance. The rapid reversion after insulin treatment excludes the possibility that streptozotocin in itself causes the ISO resistance and points towards a direct insulin effect on myocardial catecholamine sensitivity in diabetic rats. The phenomenon described might elucidate pathogenetic mechanisms behind toxic myocardial cell degeneration and may possibly have relevance for acute cardiovascular complications in diabetic patients.

The adrenergic beta-receptor adenylate cyclase system in heart and lymphocytes from streptozotocin-diabetic rats. In vivo and in vitro evidence for a desensitized myocardial beta-receptor

The myocardial beta-receptor adenylate cyclase system was investigated in short-term streptozotocin-diabetic rats. Earlier reports of a decreased sensitivity of the myocardium to isoproterenol (ISO) in these animals were elucidated by measuring the in vivo production of cAMP after ISO. A substantial decrease was seen in diabetic animals compared with controls and starved animals, and thyroxine treatment, known to sensitize the myocardium to catecholamines, did not normalize the response. The desensitization was retained in a membrane fraction in such a way that ISO was unable to increase the cAMP production while stimulation via the nucleotide-binding protein (with NaF or GTP) leads to a normal cAMP response. As the beta-adrenergic receptor number and affinity turned out to be identical in control and diabetic animals, a functional uncoupling of the myocardial beta-receptor from productive adenylate cyclase activation seems thus to exist in experimental diabetes. It is unlikely that it has anything to do with the thyroid status of the animals, but the possibility of a catecholamine-induced densensitization cannot be excluded. The phenomenon is not universal as the beta-receptor-adenylate cyclase system is normal in isolated spleen lymphocytes. Whether the described phenomenon obtained in an animal study has any relevance for the increased incidence of heart failure in human diabetes mellitus is not known at present.

Decreased myocardial calcium uptake after isoproterenol in streptozotocin-induced diabetic rats. Studies in the in vitro perfused heart

Myocardial calcium uptake in response to isoproterenol (ISO, 10(-4) M) was investigated in control and streptozotocin-induced diabetic rats using an in vitro heart perfusion model. An initial labeling with 45Ca added to the perfusate (with or without ISO) was followed by a cold calcium-free washout, thus clearing the myocardial interstitium of 45Ca. In this way the remaining 45Ca was an estimate of the myocardial calcium uptake during the labeling period. In control rats ISO induced a statistically significant increase in myocardial calcium uptake within the first 5 minutes, as well as from the 5th to the 15th minutes after exposure to this strong beta-receptor agonist. In contrast to this, diabetic hearts showed no increase in calcium uptake during any of these periods. The toxic effect of ISO was expressed by a leak of creatinine phosphokinase to the perfusate. In control rats the concentration of creatinine phosphokinase increased after ISO with a statistically significant correlation to the calcium uptake, whereas no enzymatic leak was seen after perfusion of the diabetic hearts. This abnormal response to strong beta-receptor stimulation in experimental diabetes is in accordance with our earlier in vivo finding of a myocardial protection against toxic doses of ISO. These results indicate a decreased catacholamine-induced calcium transport through the myocardial sarcolemma in streptozotocin-induced diabetic rats. This might hypothetically have relevance for diabetic heart disease as well as diabetic neuropathy.

Lack of cardiotoxic effect of isoproterenol in streptozotocin diabetic rats. A morphometric study of isoproterenol induced fibrosis

The well known cardiotoxic effect of isoproterenol (ISO) was investigated in normal and streptozotocin diabetic rats. Seven days after the subcutaneous injection of ISO (15 mg/kg) the hearts were perfusion fixed and 12 sections from each heart were stained (Masson's trichrome). ISO induced myocardial fibrosis was quantified at the light microscopic level according to established morphometric principles. Pulse rate and ST elevation were recorded by EEC (3 standard leads) before and after the ISO injection. Non-diabetic control animals showed marked fibrosis after ISO, but surprisingly the diabetic animals showed no fibrosis after ISO treatment. These findings were in accordance with an ISO induced ST elevation seen only among control animals although both groups showed the same degree of tachycardia. Insulin treatment prevented the protection against ISO and when streptozotocin was injected 24 h after the ISO a normal quantitative and qualitative appearance of the scar tissue was seen. It thus seems that streptozotocin diabetic rats are protected against the toxic effect of ISO, leaving the haemodynamic response unaffected. Which factor in the diabetic metabolism is responsible for the present phenomenon is not known, but a defect in the signal transmission from the beta-receptor to the adenylcyclase is suggested as a possible explanation.

Irreversibility of glomerular basement membrane accumulation despite reversibility of renal hypertrophy with islet transplantation in early experimental diabetes

A quantitative morphologic study of the glomeruli in rats after 4 wk of streptozotocin-induced diabetes showed a number of glomerular changes, as previously described. Of particular interest was the increase in the total amount of glomerular basement membrane material [from 0.94 +/- 0.13 (SD) mm3 to 1.26 +/- 0.14 mm3 per kidney]. This parameter did not change after 4 wk of normoglycemia following islet cell transplantation (1.19 +/- 0.17 mm3), nor was the total glomerular volume normalized. The contralateral kidney was weighed and used for estimating the total amounts of protein, RNA, and DNA. Four weeks of diabetes expectedly resulted in a 50% increase in kidney weight, and islet cell transplantation diminished this to 15% in excess of normal. The average cell size (protein/DNA ratio) paralleled the kidney size after diabetes and following transplantation. The average amount of RNA per cell (RNA/DNA) increased significantly after induction of diabetes and was totally normalized after transplantation. Kidney protein concentration (mg protein/mg kidney) remained constant throughout the experiment. Considering that a few weeks of diabetes provokes a large increase in basement membrane material, it is especially noteworthy that 1 mo of normoglycemia is quite insufficient to reverse the accumulation.

The rate of synthesis and breakdown of glomerular basement membrane material at the transition 'normal to diabetes' and 'diabetes to normal'

A considerable enlargement of the renal glomeruli is present very early after the acute onset of juvenile diabetes mellitus. In the hypertrophied glomeruli the surface area of the capillary walls, the filtration surface, is increased, and thereby also the amount of basement membrane in the capillary wall. The rate of development of this type of diabetic basement membrane accumulation has been studied in streptozotocin diabetic rats with 4- and 47-day duration of diabetes. During the first 4 days a 40% increase in the total amount of peripheral basement membrane material occurs, whereas the following period up to 47 days shows no further change. The structural changes of the glomerular capillaries seen in conjunction with the basement membrane accumulation comprise an enlargement of the filtration surface and capillary luminal volume. In another experiment, 4-week diabetic animals were transplanted with pancreatic islets. The renal structures were studied quantitatively after 4 weeks of normalization. It was found that the increased amounts of basement membrane material were still present.