Images in cardiovascular medicine. Intravascular ultrasound for stent implantation in aortic dissection.
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Aortic Dissection↗
Biomedical subjects
T Meinertz
Publications and source records attributed to T Meinertz.
Diurnal variations of the ventricular pacing threshold in patients with cardiac pacemakers are not related to changes in autonomic tone.
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Aged↗
Usefulness of carvedilol in unstable angina pectoris.
The safety and efficacy of adding oral carvedilol (25 mg twice daily) to standardized treatment of unstable angina was assessed in a multicenter, randomized, double-blind, placebo- controlled trial on 116 patients with acute unstable angina. Patients were monitored in an intensive care unit and underwent 48-hour Holter monitoring to assess transient ischemia. Carvedilol as adjunctive therapy resulted in a significant reduction of median heart rate (65 vs 75 beats/min, p <0.05), mean systolic blood pressure (133 vs 130 mm Hg, p <0.05), and mean rate-pressure product (8,337 vs 10,042, p <0.05). Carvedilol reduced the ischemic burden during 48 hours of treatment by 75% (49 vs 204 minutes), including a 36% reduction of patients with ischemic episodes (p <0.05), a 66% reduction of the mean number of ischemic episodes (8 vs 24, p <0.05), and a 76% reduction in the mean duration of ischemic episodes (50 vs 205 minutes, p <0.05). Side effects occurred in 8 of 59 patients (13.6%) in the carvedilol group and in 5 of 54 patients (8.8%) given placebo. Although not significant, the early onset of maximal blood pressure reduction and the delayed effect on heart rate were closely correlated to drug-induced hypotension and bradycardia in the carvedilol group. Thus, carvedilol as an adjunctive to standardized treatment effectively reduces heart rate and blood pressure, and thus the ischemic burden in patients with unstable angina pectoris, but requires close monitoring of patients at risk for bradycardia or hypotension.
Acute Disease↗
[Myocardial revascularization for therapy-refractory angina pectoris in the elderly].
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Aged↗
Tetrahydrobiopterin improves endothelium-dependent vasodilation in chronic smokers : evidence for a dysfunctional nitric oxide synthase.
Conditions associated with impaired nitric oxide (NO) activity and accelerated atherosclerosis have been shown to be associated with a reduced bioavailability of tetrahydrobiopterin (BH4). We therefore hypothesized that BH4 supplementation may improve endothelial dysfunction of chronic smokers. Forearm blood flow (FBF) responses to the endothelium-dependent vasodilators acetylcholine (ACh; 0.75, 1.5, and 3.0 microg/100 mL tissue/min) or serotonin (5-HT; 0.7, 2.1, and 6.3 ng/100 mL tissue/min), to the inhibitor of endothelial nitric oxide synthase (NOS) N(G)-monomethyl-L-arginine (L-NMMA; 2, 4, and 8 micromol/min), and to the endothelium-independent vasodilator sodium nitroprusside (SNP; 0.1, 0.3, and 1.0 microg/100 mL tissue/min) were measured by venous occlusion plethysmography in controls and chronic smokers. Drugs were infused into the brachial artery, and FBF was measured before and during concomitant intra-arterial infusion of BH4, tetrahydroneopterin (NH4; another reduced pteridine), or the antioxidant vitamin C (6 and 18 mg/min). In control subjects, BH4 had no effect on FBF in response to ACh, 5-HT, and SNP. In contrast, in chronic smokers, the attenuated FBF responses to ACh and 5-HT were markedly improved by concomitant administration of BH4, whereas the vasodilator responses to SNP were not affected. L-NMMA-induced vasoconstriction was significantly reduced in smokers compared with controls, suggesting impaired basal NO bioactivity. BH4 improved L-NMMA responses in smokers while having no effect on L-NMMA responses in controls. Pretreatment with vitamin C abolished BH4 effects on ACh-dependent vasodilation. In vitro, NH4 scavenged superoxide created by the xanthine/xanthine oxidase reaction equipotent like BH4 but failed to modify ACh-induced changes in FBF in chronic smokers in vivo. These data support the concept that in addition to the free radical burden of cigarette smoke, a dysfunctional NOS III due to BH4 depletion may contribute at least in part to endothelial dysfunction in chronic smokers.
Acetylcholine↗
Effects of long-term nitroglycerin treatment on endothelial nitric oxide synthase (NOS III) gene expression, NOS III-mediated superoxide production, and vascular NO bioavailability.
Long-term nitroglycerin (NTG) treatment has been shown to be associated with cross-tolerance to endothelium-dependent vasodilators. It may involve increased production of reactive oxygen species (such as superoxide, O(2)(.-)) that rapidly inactivate the nitric oxide (NO) released from the endothelial cells. It remains to be elucidated, however, whether long-term treatment with NTG alters the activity and expression of the endothelial NO synthase (NOS III) and whether this enzyme can contribute to O(2)(.-) formation. We studied the influence of long-term NTG treatment on the expression of NOS III as assessed by RNase protection assay and Western blot. Tolerance was measured ex vivo in organ chamber experiments with rat aortic rings. O(2)(.-) and NO formation were quantified using lucigenin- and Cypridina luciferin analog-enhanced chemiluminescence as well as electron spin resonance (ESR) spectroscopy. Treatment of Wistar rats with NTG (Alzet osmotic minipumps, NTG concentration 10 microg x kg(-1) x min(-1)) for 3 days caused marked tolerance, cross-tolerance to the endothelium-dependent vasodilator acetylcholine, and a significant increase in O(2)(.-)-induced chemiluminescence. Tolerance was associated with a significant increase in NOS III mRNA to 236+/-28% and NOS III protein to 239+/-17%. In control vessels, the NOS inhibitor N(G)-nitro-L-arginine (L-NNA) increased the O(2)(.-)-mediated chemiluminescence, indicating that basal production of endothelium-derived NO depresses the baseline chemiluminescence signal. In the setting of tolerance, however, L-NNA decreased steady-state O(2)(.-) levels, indicating the involvement of NOS III in O(2)(.-) formation. Likewise, A23187-induced, NOS III-mediated O(2)(.-) production was more pronounced in tolerant than in control vessels. Vascular NO bioavailability as assessed with ESR spectroscopy using iron-thiocarbamate as a trap for NO was significantly reduced in tolerant vessels. Pretreatment of tolerant tissue in vitro with the protein kinase C (PKC) inhibitors reduced basal and stimulated NOS III-mediated O(2)(.-) production and partially reversed vascular tolerance. These findings suggest that NTG treatment increases the expression of a dysfunctional NOS III gene, leading to increased formation of O(2)(.-) and decreased vascular NO bioavailability. Normalization of NOS III-mediated O(2)(. -) production and improvement of tolerance with PKC inhibition suggests an important role for PKC isoforms in mediating vascular dysfunction caused by long-term NTG treatment.
Acetylcholine↗
Initial experience with a hydrophilic-coated guidewire for recanalization of chronic coronary occlusions.
Chronic coronary occlusions are still a therapeutic challenge to the interventional cardiologist. New techniques such as laser wire have improved recanalization rates, but outcomes are still far from satisfactory. We report the results of a nonrandomized single-center investigation using a hydrophilic-coated guidewire (Terumo Crosswire). Between September 1996 and September 1998, 107 chronic occlusions in 106 patients were approached when previous attempts with conventional guidewires failed. Median occlusion duration in these cases was 4 months (range, 0.5-122); mean occlusion length was 19 +/- 11 mm (range, 5-60). Forty-five (42%) of these attempts were successful. Attempts were successful in 42% in the left anterior descending artery, in 30% in the left circumflex artery, in 48% in the right coronary artery, and in 43% in coronary artery bypass grafts. Success rates ranged from 56% for occlusions of less than 4-month duration to 18% for occlusions of more than 36-month duration. The success rate in TIMI 1-flow lesions was significantly higher than in TIMI 0 flow lesions, 85% vs. 36%. In a multivariate regression analysis, TIMI flow grade and occlusion age were independent predictors of success. There were no deaths or Q-wave myocardial infarctions; two cases of hemopericardium were treated successfully. In five cases, pericardial contrast staining due to vessel perforation occurred. Our results indicate that the Crosswire is an effective tool in the treatment of chronic coronary occlusions, even when recanalization attempts with conventional guidewires fail. Cathet. Cardiovasc. Intervent. 49:45-50, 2000.
Adult↗
Oxidative stress increases synthesis of big endothelin-1 by activation of the endothelin-1 promoter.
Modulation of the biosynthesis of the vasoconstrictor peptide endothelin-1 by oxygen-derived free radicals generated by xanthine oxidase or hydrogen peroxide was studied in cultured endothelial cells. Endothelin-1 metabolism was investigated at the level of endothelin-1 promoter, preproendothelin-1 mRNA and intracellular big endothelin-1. Endothelin-1 mRNA, as characterized by Northern blotting, was increased both time- and dose-dependently by xanthine oxidase to up to 500% above baseline. Analysis of endothelin-1 promoter activity using a construct containing 1329 bp of the endothelin-1 promoter revealed that promoter activity was increased up to eight-fold by incubation with xanthine oxidase. Specificity was ascertained by co-incubation with superoxide dismutase and catalase leading to inhibition of the effect of xanthine oxidase. A significant contribution of nitric oxide was ruled out, since NOS III-mRNA transcription remained unchanged and l -NAME did not significantly alter endothelin-1 promoter activity. Synthesis of intracellular big endothelin-1 protein was increased dose-dependently by xanthine oxidase. Our results indicate that oxidative stress leads to increased endothelial synthesis of big endothelin-1, which is a previously unknown mechanism and may help to understand the detrimental association of increased oxidative stress and elevated endothelin-1 levels in pathophysiological conditions promoting atherosclerosis.
Animals↗
Tetrahydrobiopterin improves endothelium-dependent vasodilation by increasing nitric oxide activity in patients with Type II diabetes mellitus.
AIMS/HYPOTHESIS: Tetrahydrobiopterin is an essential cofactor of nitric oxide synthase, and its deficiency decreases nitric oxide bioactivity. Our aim was to find whether supplementation of tetrahydrobiopterin could improve endothelial dysfunction in diabetic patients. METHODS: Forearm blood flow responses to the endothelium-dependent vasodilator acetylcholine (0.75-3.0 microg x 100 ml(-1) x min(-1)) and to the endothelium-independent vasodilator sodium nitroprusside (0.1-1.0 microg x 100 ml(-1) x min(-1)) before and during concomitant intra-arterial infusion of tetrahydrobiopterin (500 microg/min) were measured by venous occlusion plethysmography in 12 control subjects and 23 patients with Type II (non-insulin-dependent) diabetes mellitus. RESULTS: In control subjects, tetrahydrobiopterin had no effect on the dose-response curves to acetylcholine and sodium nitroprusside. In contrast, in diabetic patients, the attenuated endothelium-dependent vasodilation to acetylcholine was considerably improved by concomitant treatment with tetrahydrobiopterin, whereas the endothelium-independent vasodilation was not affected. This beneficial effect of tetrahydrobiopterin in diabetic patients could be completely blocked by N(G)-monomethyl-L-arginine. CONCLUSION/INTERPRETATION: These findings suggest the possibility that endothelial dysfunction in Type II diabetes might be related to decreased availability of tetrahydrobiopterin.
Acetylcholine↗
Impact of intravascular ultrasound guidance on directional coronary atherectomy.
In contrast to the luminogram of coronary angiography, intravascular ultrasound (IVUS) has proven to accurately assess both coronary lumen and vessel morphology due to its 360 degrees imaging capacity. Directional coronary atherectomy (DCA) improves the coronary lumen by removing plaque mass rather than stretching the vessel and compressing the plaque as with conventional percutaneous transluminal coronary angioplasty. In an attempt to optimize the procedural result of DCA we prospectively investigated the impact of IVUS guidance in a head to head comparison to on-line quantitative coronary angiography (QCA) on the result of DCA. In 16 consecutive patients IVUS demonstrated significant residual plaque mass after DCA irrespective of a satisfactory angiographic result. After a mean of 9 +/- 2 cuts luminal improvement was obtained with an area stenosis by angiography of 39 +/- 17% and by IVUS of 50 +/- 10% (p < 0.05), a diameter stenosis by angiography of 23 +/- 10% and IVUS of 35 +/- 14% (p < 0.05) and finally a minimal lumen diameter (MLD) by angiography of 2.9 +/- 0.5 mm and by IVUS of 2.3 +/- 0.5 mm (p < 0.005). After both on-line QCA and IVUS measurements a second series of 7 +/- 2 cuts were initiated to debulk more atheroma and improve stenosis dimensions. After additional cuts IVUS revealed further luminal improvement with an area stenosis by angiography of 25 +/- 16% and IVUS of 21 +/- 18% (n.s.), a diameter stenosis by angiography of 16 +/- 11% and by IVUS of 13 +/- 19% (n.s.) and finally a MLD by angiography of 3.1 +/- 0.5 mm and by IVUS of 2.8 +/- 0.3 mm (p < 0.05). Intraprocedural use of IVUS is superior to on-line QCA to assess the immediate result of DCA. IVUS-guided DCA results in more effective atheroma debulking than luminographic evaluation. Results of larger follow-up studies are needed to substantiate the intraprocedural advantage of IVUS with DCA.
Adult↗
[Intravenous coronary angiography with synchrotron radiation].
INTRODUCTION: Coronary artery disease still remains the primary cause of death in the western industrialized world. Although the clinical value of selective coronary angiography (SCA) is beyond dispute, the associated risk of an invasive approach, the inherent costs and the necessary hospitalization have lead to the development and investigation of novel non-invasive techniques for coronary imaging. Intravenous coronary angiography (ICA) has been shown to permit non-invasive imaging of the coronary arteries. METHODS: In 66 pts (80% male, age 62 (+/- 8.5 yrs) after interventional therapy/CABG operation, ICA and a SCA were carried out within a time interval of < 6 weeks. After determination of the individual circulation time, contrast media (370 mg iodine/ml, 15 ml/s, 21 ml) was injected via a sheath in the cubital vein while the patient was sitting in an upright position in a specially designed scanning chair. In two different projections 6-8 images/patient were obtained for further image processing and evaluation. 182 target vessels had to be evaluated (LAD 55, Cfx 21, RCA 54, Grafts 52). In 50 target vessels one or more stents were implanted. RESULTS: 182 target vessels were evaluated according to the following criteria: no stenosis, < 70%, > = 70%, occlusion. Evaluation of the ICA and SCA images was performed by two independent investigators. Due to poor image quality, 17 vessels were not evaluated. The ICA findings were compared to that of SCA. For the LAD a sensitivity of 84% (specificity 93%), for the RCA a sensitivity of 85% (specificity 97%), for the Cfx a sensitivity of 67% (specificity 90%), and for grafts a sensitivity of 85% (specificity 97%) was calculated. CONCLUSION: ICA proved to be a feasible and safe technique for follow-up after coronary intervention/CABG operation on an outpatient basis. Evaluation of stents and severe calcification is possible. A good image quality provided, LAD RCA and grafts can be evaluated with an acceptable sensitivity and specificity. Due to superimpositioning the low sensitivity for the Cfx has to be compensated by further image processing.
Aged↗
Six-month clinical and angiographic outcome after successful excimer laser angioplasty for in-stent restenosis.
OBJECTIVES: This study evaluated the clinical and angiographic six-month follow-up after excimer laser coronary angioplasty (ELCA) for restenosed coronary stents. BACKGROUND: Excimer laser coronary angioplasty has recently been shown to be safe and efficient for the treatment of in-stent restenosis. METHODS: Ninety-six consecutive patients successfully treated with ELCA within 141 stents were included in a six-month clinical and angiographic follow-up. RESULTS: During follow-up there was one sudden death and one patient with documented myocardial infarction. Angina pectoris classified as > or = Canadian Cardiovascular Society II reoccurred in 49 patients. Follow-up angiography was obtained in 89 patients (93%) with 133 stents. Quantitative coronary angiography revealed a mean diameter stenosis of 77 +/- 10% before intervention, 41 +/- 12% after laser treatment and 11% +/- 12% after adjunctive percutaneous transluminal coronary angioplasty (p < 0.001). Six months after ELCA the mean diameter stenosis had increased to 60 +/- 26% (p < 0.001). A > or =50% diameter stenosis was present in 48 patients (54%); in 24 of these patients diameter stenosis was > or =70%. Total occlusions occurred in an additional 10 patients (11%). There was a trend toward an increased recurrent restenosis rate in patients with diabetes mellitus and long lesions or total occlusions (p = 0.059). Forty-eight patients (50%) received medical treatment after six months. Reinterventions were necessary in 30 patients (31%), and coronary artery bypass surgery was performed in 17 patients (18%). Event-free survival was 50%. CONCLUSIONS: Excimer laser angioplasty for in-stent restenosis was associated with a high incidence of recurrent restenosis in this group of patients, suggesting that this technique is unlikely to reduce recurrent in-stent restenosis and that other approaches are necessary.
Adult↗
Effects of a nitrate-free interval on tolerance, vasoconstrictor sensitivity and vascular superoxide production.
OBJECTIVES: In the present study, we tested whether a nitrate-free interval is able to prevent increases in vascular superoxide (O2*-) and the development of hypersensitivity to vasoconstrictors and whether this may result in restoration of vascular nitroglycerin (NTG) sensitivity. BACKGROUND: Intermittent NTG-patch treatment (12 h patch on/patch-off) has been shown to increase ischemic periods in patients with stable coronary arteries, suggesting a rebound-like situation during the patch-off period. Recently, we demonstrated that long-term treatment with NTG induces tolerance, which was in part related to increases in vascular O2*- and increased vasoconstrictor sensitivity. METHODS: New Zealand white rabbits received a continuous application of NTG patches (0.4 mg/h) or an intermittent application of NTG patches (12 h patch on, 12 h patch off) for three days. Isometric tension studies were performed with aortic rings, and vascular O2*- was estimated using lucigenin-derived chemiluminescence (5 micromol/liter). Expression of the copper/zinc (Cu/Zn) superoxide dismutase (SOD) was assessed by Western blotting, and SOD activity was measured by autooxidation of 6-hydroxydopamine. RESULTS: Continuous treatment with NTG caused tolerance to NTG, cross-tolerance to the endothelium-dependent vasodilator acetylcholine, increased vascular O2*-, reduced Cu/Zn SOD expression and increased sensitivity to vasoconstrictors such as phenylephrine, serotonin and angiotensin II. On/off treatment with NTG improved tolerance, corrected endothelial dysfunction and decreased vascular O2*-. In addition the reduction in SOD expression was less pronounced, whereas increases in the sensitivity to vasoconstrictors such as phenylephrine and serotonin remained nearly unchanged. CONCLUSIONS: Enhanced vasoconstrictor sensitivity may explain, at least in part, the rebound phenomena observed in patients during a 12-h NTG patch-off period.
Acetylcholine↗
Survival and prognosis: investigation of Crataegus extract WS 1442 in congestive heart failure (SPICE)--rationale, study design and study protocol.
UNLABELLED: SPICE is the first, international, randomized, placebo-controlled, double-blind study to investigate the influence of the herbal drug Crataegus Special Extract WS 1442 (hawthorn leaves with flowers) on mortality of patients suffering from congestive heart failure. BACKGROUND: In vitro and experimental animal studies have suggested the following pharmacological modes of action of standardized Crataegus extracts: (1) cAMP-independent positive inotropy; (2) peripheral and coronary vasodilation; (3) protection against ischemia-induced ventricular arrhythmias; (4) antioxidative properties; and (5) anti-inflammatory effects. STUDY DESIGN: In this randomized, placebo-controlled, double-blind, international trial (approximately 120 investigational centers in seven European countries), up to 2300 patients with congestive heart failure, New York Heart Association class II and III and markedly impaired left ventricular function, will be enrolled and treated over a period of 24 months. During this time patients receive either two film-coated tablets of 450 mg of the Special Extract WS 1442 standardized to 84.3 mg of oligomeric procyanidines or matched placebo per day in addition to standard therapy for congestive heart failure, such as diuretics, digoxin or digitoxin, beta-adrenoceptor blockers and angiotensin-converting-enzyme inhibitors. The primary outcome variable is the combined endpoint of cardiac death, non-lethal myocardial infarction, and hospitalization due to progression of heart failure. Secondary outcome variables are total mortality, exercise duration, echocardiographic parameters, quality of life as well as pharmacoeconomic parameters. The first patient was included in October 1998. The trial is expected to be completed at the end of 2002.
Adult↗
Effects of a thin-sized lead body of a transvenous single coil defibrillation lead on ICD implantation. Kainox RV Study Group.
In the interest of patients receiving implantable cardioverter defibrillators (ICDs), the clinical benefits of newer and thinner transvenous defibrillation leads have to be determined. The aims of this study were to evaluate the ICD procedure duration and the frequency of lead dislocation at the 3-month follow-up of a new defibrillation lead with a thin-sized lead body and its conventional-sized predecessor. The thin-sized single coil defibrillation lead (Kainox RV, Biotronik; lead body 6.7 Fr) was implanted in 61 patients and the conventional-sized defibrillation lead (SPS, Biotronik; lead body 7.8 Fr) in 60 patients. Both leads were connected to a left-sided, prepectorally implanted Phylax ICD (Biotronik) with active housing. The lead implantation time and total procedure duration were determined. Lead implantation time was defined as the time from lead insertion to the end of the pacing measurements. The total procedure duration spanned skin incision to closure. The incidence of lead repositioning during the lead implantation time and during ventricular fibrillation conversion testing was also assessed. The frequency of lead dislocations was recorded at the 3-month follow-up. Mean lead implantation time and total procedure duration of the thin-sized lead (23 +/- 22 minutes 76 +/- 37 minutes) were not statistically different from the time needed for the conventional-sized lead (22 +/- 20 minutes 81 +/- 34 minutes). The number of lead repositionings during the lead implantation time was similar (thin-sized lead: 1.4 +/- 2.4; conventional-sized lead: 1.1 +/- 1.9). An additional lead repositioning was not necessary during ventricular fibrillation conversion testing in 93.4% of the patients with thin-sized and in 94.4% with conventional-sized leads (not significant). At the 3-month follow-up, there were four (6.6%) lead dislocations in the thin-sized and four (6.7%) in the conventional-sized lead group. In conclusion, the down-sized lead body of the new defibrillation lead influenced neither ICD procedure duration nor the incidence of lead dislocation during follow-up.
Case-Control Studies↗
Catheter ablation of atrial flutter guided by electroanatomic mapping (CARTO): a randomized comparison to the conventional approach.
INTRODUCTION: Three-dimensional electroanatomic (CARTO) activation mapping of the cavotricuspid isthmus can be helpful to guide atrial flutter ablation, but to date has not been investigated in comparison to conventional strategies. The aim of the present study was to assess the efficacy of the CARTO navigation system, especially with respect to the fluoroscopy time required for successful atrial flutter ablation. METHODS AND RESULTS: Eighty patients with recurrent common-type atrial flutter were randomly assigned to temperature-controlled radiofrequency (RF) catheter ablation, either guided by conventional criteria (group 1) or additionally oriented on electroanatomic mapping (group 2). In all patients, similar multipolar catheters were inserted into the coronary sinus and placed at the tricuspid annulus, respectively. In group 2, positioning of the mapping electrode and delivery of RF pulses within the cavotricuspid isthmus was mainly oriented on the CARTO map to achieve the most linear and continuous RF lesions. Abolition of intra-atrial conduction verified by conventional criteria (group 1) and electroanatomic mapping (group 2) could be verified in all patients. The overall number of RF pulses (group 1: 16.7+/-6.5; group 2: 13.2+/-5.3) and mean procedure duration (group 1: 172.5+/-47.4 min; group 2: 169.3+/-47.3 min) were not different between the two groups, but mean fluoroscopy time was significantly shorter when the CARTO technology was used (group 1: 29.2+/-9.4 min; group 2: 7.7+/-2.8 min; P = 0.0001). Recurrence of atrial flutter was observed in 3 (9%) patients in each group after a mean follow-up of 8.5+/-2.8 months. CONCLUSION: Atrial flutter can be abolished effectively using the conventional technique as well as oriented on electroanatomic mapping. However, overall X-ray exposure can be significantly reduced by the CARTO-guided approach without prolongation of procedure duration.
Aged↗
Efficacy of single lead VDD pacing in patients with impaired and normal left ventricular function.
Atrial synchronous ventricular pacing seems to be the best pacing mode for patients with advanced AV block and impaired LV function. The long-term follow-up of single lead VDD pacing was studied in 33 patients with impaired LV function and compared to 42 patients with normal LV function. All patients received the same VDD lead and VDDR pacemaker. The lead model with 13-cm AV spacing between the atrial and ventricular electrode was implanted in 89% of the patients. Follow-ups were 1, 3, 6, and 12 months after implantation. The percentage of atrial sensing and the P wave amplitude were determined at each follow-up. Minimal P wave amplitude at implantation was 2.0 +/- 1.4 mV in patients with impaired and 1.7 +/- 0.9 mV with normal LV function (not significant). At the 12-month follow-up, 33 patients with normal and 23 patients with depressed LV function remained paced in the VDD mode. The remaining patients died in five (impaired LV function) and seven cases (normal LV function) or their pacemakers were programmed to the VVI/VVIR pacing mode in four (impaired LV function) and three cases (normal LV function). P wave amplitude did not differ in the two groups (e.g., at month 12: impaired: 1.17 +/- 0.42 mV; normal: 1.09 +/- 0.49 mV). The atrial sensitivity was programmed in most patients to sensitive settings with no differences between the two groups (e.g., at month 12: impaired: 0.13 +/- 0.06 mV; normal: 0.13 +/- 0.05 mV). The diagnostic counters indicated nearly permanent atrial sensing (e.g., at month 12: impaired: 99.3 +/- 2.2%; normal: 99.0 +/- 1.0 mV). In conclusions, single lead VDD pacing restored AV synchronous ventricular pacing in patients with normal and with impaired LV function indicating that it could be an alternative to DDD pacemakers, but not to dual-chamber pacing.
Aged↗
Automatic threshold tracking activation without the intraoperative evaluation of the evoked response amplitude. AUTOCAP Investigators.
Automatic threshold tracking (Autocapture) controls the amplitude of the pacing pulse and adjusts it to the actual pacing threshold. The algorithm is based on the proper detection of the evoked response (ER) amplitude after the pacing pulse. For this reason an intraoperative evaluation of ER and polarization is recommended. The aims of the study were to evaluate the ER signal and polarization and the performance of automatic threshold tracking without any intraoperative testing of the ER signal. In addition, the ER amplitude was correlated with the pacing threshold, pacing impedance, spontaneous R wave amplitude, and with the clinical data. The study included 60 patients who received the VVIR pacemaker Regency connected to the Membrane E 1450/1452 pacing lead (St. Jude-Pacesetter). At implantation, a pacing threshold < 0.7 V at 0.5 ms was achieved in all patients. ER and polarization were assessed for the first time at hospital predischarge testing. Follow-up measurements were conducted at month 1, 3, and 6. The ER amplitude at hospital discharge was 8.4 +/- 4.2 mV and increased to 9.4 +/- 4.8 mV at the 6-month follow-up. The pacemaker recommended not to program automatic threshold tracking on in one patient permanently and in three patients intermittently. The ER amplitudes were not differently distributed in men compared with women or in right-sided compared to left-sided implants. The correlation between age and the evoked response was r = 0.15. The correlation between ER amplitude and pacing threshold was r = -0.08, with pacing impedance r = 0.02, and with R wave amplitude r = 0.44. In conclusion, despite no operative evaluation of the ER amplitude being performed, the mean ER amplitude was about 9 mV at 6-month follow-up. Automatic threshold tracking could be programmed on in 93% of the patients throughout the time. Neither the clinical data nor the conventional electrical parameters help to predict patients who will have low ER amplitude or to optimize the ER signal at implantation.
Aged↗