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Biomedical subjects

O J Ohm

Publications and source records attributed to O J Ohm.

At least 19 recordsLinked to original sources
PubMed1992

[Sudden cardiac death].

Sudden cardiac death is instant unexpected death that occurs within one hour of an abrupt change in a person's stable clinical state. The mechanism is generally a ventricular tachyarrhythmia. The underlying pathology is usually coronary heart disease. In 1990, 18 patients who survived sudden cardiac death, excluding those with acute myocardial infarction, were evaluated and treated in our institution. 15 patients had coronary heart disease, one had hypertrophic cardiomyopathy, one had dilated cardiomyopathy and one had a replaced aortic valve. Evaluation included heart catheterization and electrophysiological examination. Treatment was specifically tailored to each patient according to etiology, results of all tests and the patient's prognostic factors. Treatment included a permanent pacemaker-cardioverter-defibrillator, antiarrhythmic drug therapy, aortocoronary bypass and betablocker therapy.

Aged↗
PubMed1992

[Intermittent bradyarrhythmia in infants and small children treated with permanent pacemaker].

Four children aged two, two and four months and five years respectively, with intermittent cardiac bradyarrhythmias and otherwise normal hearts are described. The diagnoses were based upon findings by telemetry and 24-hour ECG-recordings. Two patients had sinus node disease, one patient had intermittent complete atrioventricular block, and the fourth had a permanent first degree atrioventricular block and intermittent high grade second degree atrioventricular block. All patients presented serious symptoms with apparent life-threatening events before admission. They were given a permanent cardiac pacemaker. One patient experienced recurrent excessive increase in the myocardial stimulation threshold, leading to further syncopal episodes. All patients are developing adequately with normally functioning pacemakers.

Bradycardia↗
PubMed1992

Efficacy of automatic multimodal device therapy for ventricular tachyarrhythmias as delivered by a new implantable pacing cardioverter-defibrillator. Results of a European multicenter study of 102 implants.

BACKGROUND: Third-generation implantable cardioverter-defibrillators are devices designed to treat ventricular tachycardia (VT) and ventricular fibrillation (VF) by means of overdrive pacing, cardioversion, or defibrillation. So far, the efficacy of tiered therapy has been documented only in small series. Therefore, a European multicenter clinical evaluation study of a new tachyarrhythmia control device, the Medtronic PCD pacer-cardioverter-defibrillator with epicardial patch-lead configuration, was undertaken. METHODS AND RESULTS: We report on 102 patients (mean age, 55 +/- 13 years) from 11 European centers. PCD devices implanted between May 1989 and February 1991 were included. The patients suffered from hemodynamically significant ventricular tachyarrhythmias not suppressed by antiarrhythmic drug therapy and unrelated to acute myocardial infarction; one patient had nonsustained VT and severely depressed left ventricular function. Seventy patients had coronary artery disease with old myocardial infarctions, 23 had cardiomyopathies of various etiologies, and nine patients had no detectable heart disease. Mean ejection fraction was 36 +/- 14% (range, 10-76%). Mean intraoperative defibrillation threshold (51 patients) was 10.6 +/- 5.1 J (range, 2-18 J). The documented follow-up ranged from 1 to 21 months (mean, 9.4 +/- 5.8 months), or 79.9 cumulative patient-years. Perioperative mortality was 3.9%. The actuarial survival rate at 12 months was 91%. One sudden arrhythmic death occurred. Sixty patients (58%) received device therapy. Seventeen patients had therapies only for "VF" episodes, 16 patients only for VT, and 28 patients for VT and "VF" episodes. Based on device memory data, 1,235 spontaneous VT episodes were detected and treated in 43 patients. Twelve hundred four of these VT episodes received painless initial antitachycardia pacing therapy, restoring sinus rhythm in 91%. The 108 ongoing episodes received 209 multiple therapeutic attempts. Eighty-five additional overdrive pacing therapies restored sinus rhythm in 30%. Initial ineffective antitachycardia pacing therapies received 51 cardioversion pulses. The success rate was 61%. Seventy-three additional cardioversion pulses were delivered to backup ineffective pacing therapy as well as ineffective secondary cardioversion pulses. Their success rate was only 40%. Two hundred eighty-six spontaneous episodes were detected in 44 patients as "VF." Overall defibrillation efficacy was 97.6%. CONCLUSIONS: The implanted device nearly eliminates sudden arrhythmic death in patients with documented, potentially fatal ventricular tachyarrhythmias. Automatic tiered therapy is highly effective to restore sinus rhythm, provided that an integrated two-zone tachycardia detection algorithm is used, assigning lower tachycardia rates to overdrive pacing and/or cardioversion and higher tachycardia rates to defibrillation. In general, spontaneous VTs can be terminated by automatic overdrive pacing, and painful or disturbing countershock therapies are not required to terminate the majority of spontaneous VT episodes.

Death, Sudden, Cardiac↗
PubMed1991

The influence of supine relaxation on blood pressure, heart rate and atrial natriuretic peptide in normal subjects.

The effect of recumbent rest on plasma atrial natriuretic peptide (ANP) concentration, mean blood pressure (MBP) and heart rate was studied in 26 normal human volunteers. Plasma ANP concentration, MBP and heart rate were determined after 10 min sitting and after 2, 5, 8, 15 and 30 min of recumbency. During the first 5 min of recumbency there were significant decreases in both MBP (p less than 0.001) and heart rate (p less than 0.001) compared with sitting. There was a small but significant fall in plasma ANP concentration (p = 0.02) after 30 min of recumbency compared with sitting. No further reduction in MBP or heart rate occurred after 5 min supine. The level of MBP following 5 min supine correlated significantly (r = 0.44; p = 0.02) with the plasma ANP concentration 25 min later. Blood pressure and heart rate are highly dependent on posture and relaxation, and plasma ANP concentration in lesser degree. It is necessary to wait for stable baseline values to develop before any comparisons between blood pressure and plasma ANP are done. If it is assumed that a causative relation exists between blood pressure and plasma ANP level, it appears there may be a delay of 20-30 min between a change in blood pressure and the physiological response of plasma ANP level. This observation may have implications for the interpretation of the relation between blood pressure and plasma ANP concentration in healthy individuals.

Adult↗
PubMed1987

A time-related study by Doppler and M-mode echocardiography of hemodynamics, heart size, and AV valvular function during activity-sensing rate-responsive ventricular pacing.

Noninvasive Doppler and M-mode echocardiography were used to: measure stroke volume (SV), left atrial (LA) size, left ventricular end-diastolic (EDD), end-systolic dimensions (ESD), left ventricular fractional shortening (FS), and for determination of mitral and tricuspid insufficiency (MI and TI) before starting and after 1, 3, and 6 months of rate-responsive ventricular pacing (RRP). The study group consisted of 13 patients (mean age, 75 years) who could be expected to benefit from an increase in cardiac output mediated by an increment of heart rate during exercise. In VVI + activity mode (RRP), the pacemaker was programmed to a basic heart rate of 60 and a maximum heart rate of 125 bpm. The SV at rest was 71 +/- 5 before RRP, and fell to 57 +/- 4 after 3 months (p less than 0.05) and to 53 +/- 4 ml/beat after 6 months of RRP (p less than .01). The LA size and ESD were unchanged during follow-up. The EDD decreased from 6.2 +/- 0.3 to 5.4 +/- 0.2 (p less than 0.002) during the first 6 months of RRP. The FS was reduced from 33 +/- 4 to 27 +/- 3% (p less than 0.02) during the first 6 months of RRP. Four of 6 patients treated previously with a VVI pacemaker (mean duration, 9 years) had MI + TI, and 3 of the 7 patients not paced previously had MI before RRP. In the last group, 1 new patient developed MI, 1 new patient developed MI + TI, and 2 patients who had MI also developed TI within 6 months of pacing. Thus, of 13 patients, 9 (69%) had either MI or MI + TI.

Aged↗
PubMed1987

Assessment of the work capacity and relationship between rate response and exercise tolerance associated with activity-sensing rate-responsive ventricular pacing.

The relationship between rate response and exercise tolerance was studied by measuring the symptom-limited maximum treadmill time (MTT)both during fixed rate VVI pacing and during VVI + activity mode pacing (RRP) in 15 patients (mean age, 73 years) who had received rate-responsive ventricular pacemakers. Their indications were atrioventricular block, sino-atrial block, and atrial fibrillation with slow ventricular response. Basic rate was programmed to 60 ppm in both pacing modes; rate response and activity threshold were programmed to 5 and medium, respectively. The order in which the two pacing modes were tested was randomly determined. The MTT was, on average, 29% longer in RRP than in VVI mode with a mean of 12 minutes in VVI and 14.8 minutes in RRP (p less than 0.001). For the subgroup of eight patients with paced-only rhythm the average increase in MTT was 38% with a mean of 9.5 minutes in VVI and 12.8 minutes in RRP (p less than 0.01). Seven patients who showed episodes of spontaneous rhythm, increased their average MTT by 17% (mean in VVI, 14.9 minutes; in RRP, 17.1 minutes; p less than 0.02). During RRP, a significant positive correlation existed between MTT and the increase in heart rate (N = 15; r = 0.83; p less than 0.001). In 12 patients with paced-only rhythm, the pacing rate remained at the programmed basic rate when the patients were lying, sitting, and standing and increased to 86 +/- 4 ppm during casual walking, and to 101 +/- 4 ppm during jumping up and down with the pacemaker programmed to the above-mentioned parameters. The maximum pacing rate during jumping corresponded with the maximum pacing rates measured from Holter recordings during normal daily activities.

Aged↗
PubMed1987

Noninvasive assessment by Doppler and M-mode echocardiography of hemodynamic responses to temporary pacing and to ventriculoatrial conduction.

A new, dual-chamber temporary pacing lead was introduced via the subclavian vein in 20 patients who needed a temporary pacemaker. Stroke volume (SV) was measured continuously by combining M-mode and noninvasive Doppler echocardiography during spontaneous rhythm (SR), AV sequential pacing at a positive AV interval (DP), ventricular pacing (VP) and AV sequential pacing at a negative AV interval (VA pacing). The valvular functions were determined by Doppler echocardiography. Left ventricular dimensions and function, and left atrial size were measured by M-mode echocardiography. In the nine patients with no valvular heart disease and with no ventriculoatrial (VA) conduction (group I) the CO increased 83 +/- 11% during DP and 42 +/- 9% during VP as compared to during SR when the heart rate (HR) was increased from 34 +/- 3 to 72 +/- 1 beats/min. The CO was 29 +/- 3% higher during DP than that during VP. In the seven patients with valvular heart disease and with no VA conduction (group II), the increment in CO compared to that during SR was 53 +/- 12% during DP and 31 +/- 11% during VP; the CO was 17 +/- 4% higher during DP than that during VP. In the four patients with spontaneous VA conduction (group III), the CO during DP was 35 +/- 10% greater than that during VP, which did not result in an increase in the CO compared to that during SR in spite of an increase in HR from 52 +/- 8 to 74 +/- 2 beats/min. The study demonstrated that DP is the preferred temporary pacing mode and also that VA conduction during VP resulted in a mean decrease of 20% in CO compared to that during VP without VA conduction. The hemodynamic benefit from DP compared to SR seems to decrease when the left ventricular end-diastolic dimension increases. Furthermore, patients with large left ventricular end-systolic dimensions seem to have a lower increase in stroke index during DP as compared to that during VP than patients with smaller end-systolic dimensions.

Aged↗
PubMed1985

A time-related study of the hemodynamic benefit of atrioventricular synchronous pacing evaluated by Doppler echocardiography.

We have used Doppler echocardiography to estimate the stroke volume (SV) in a study of 13 patients equipped with DDD pacemakers. SV was measured both during DDD and VVI pacing after observation times of 1,3,6, and 12 months of DDD pacing. SV was also measured at seven atrioventricular (AV) intervals (75-250 ms) in the search for optimal AV intervals. Mitral flow velocity was investigated to see if DDD pacing resulted in synchronous atrial contraction, and if mitral insufficiency existed at any of the pacing modes. Compared with the VVI mode, DDD pacing resulted in a mean increase in SV of 21 +/- 2% for the four observation periods. Two patients with severe left ventricular failure had no significant increase in SV during DDD vs VVI pacing. In each patient, an optimal AV interval ranging between 100-250 ms for the SV was found. Velocity profiles of mitral flow showed synchronous atrial contraction during DDD pacing, but not during VVI pacing. Mitral insufficiency was not seen in any pacing mode. DDD pacing resulted in a reduction in SV during the first 6 months, and was constant thereafter. Doppler echocardiography can be used repeatedly to evaluate the hemodynamic response of DDD pacing vs VVI pacing, and to find which AV interval gives the highest SV in the individual patient. Our study further shows that the hemodynamic benefit of DDD pacing is present after short-term as well as after long-term DDD pacing.

Adult↗
PubMed1979

Sick sinus syndrome treated with permanent pacemaker in 109 patients. A follow-up study.

During the last decade implantation of permanent pacemakers has become the treatment of choice for patients suffering from the sick sinus syndrome (SSS). We have followed up 112 SSS patients treated with permanent pacemakers in Haukeland Hospital in the period 1966--76. The pacemakers were later removed from three of the patients. In the remaining 109 patients the SSS was characterized by tachy-bradyarrhythmias (TBA) in 44 and bradyarrhythmias (BA) in 65. Before implantation, 68 patients had syncopes and 27 severe dizziness. After implantation, symptomatic improvement was apparent in 104 patients; only three still had syncopes. During the follow-up period (mean 34.4 months), 29 patients died (yearly mortality 9.3%). There was no significant difference in total mortality between patients with TBA and with BA. Concomitant disturbances in atrioventricular (AV) conduction occurred in 35.8% of the patients. Among 79 of 80 patients still alive, five had developed total AV block, 19 had stable atrial fibrillation, 12 of these were possibly pacemaker-independent (ventricular rate greater than 60/min). Systemic embolization was observed in 16 patients, more frequently in the TBA (12/44) than in the BA group (4/65) (p less than 0.001). It is concluded that permanent pacemakers have an excellent symptomatic effect in patients with SSS. The prognosis is mainly determined by the presence or absence of coronary heart disease and/or heart failure.

Adolescent↗
PubMed1979

Temporary pacemaker treatment in open heart surgery: variation in myocardial threshold, tissue and interface impedances in man.

Myocardial threshold and impedance of adequately insulated multicore metal electrodes (lengths l1 and l2) were investigated in 28 patients undergoing open heart surgery. Increase in current threshold from the pre-to postoperative period was: 607 +/- 102% (mean +/- SEM) with a constant-current pulse generator and 885 +/- 129% with a constant-voltage pulse generator. Tissue impedance (RT - initial impendance) calculated as voltage/current ratio 90 mus into the pulse changed from 564 +/- 34 omega before surgery to a minimum of 134 +/- 7 omega. Thereafter, there was a gradual increase in RT to 162 +/- 9 omega the day of electrode removal. In 25 of 28 patients the minimum values were reached the third to eighth postoperative day. Electrode/tissue interface impedances--Faraday resistance (RF) and Helmholtz capacity (CH)--were calculated from regression analysis of loaded and unloaded electrograms using the method of least squares. The RF showed a fall from 14.7 +/- 1.4 K omega to 5.2 +/- 0.3 K omega, and the CH (20-40 Hz) rose from 6.0 +/- 0.9 mu F to 15.5 +/- 0.8 muF preoperatively to the day of minimum tissue impedance. There were no further changes until the day of electrode removal. A significant positive correlation was found between CH (p < 0.002), current threshold (p < 0.005) and equivalent electrode length [lequ = l1 X l2/(l1 + l2)]. The electrode signal source impedance calculated from RT, RF and CH was of a magnitude not likely to contribute to demand failures. The low postoperative electrode impendance resulted in excessive load on the constant-voltage generator (condenser discharge type), rendering stimulation of the heart with reasonable current values impossible.

Adolescent↗
PubMed1979

The interdependence between electrogram, total electrode impedance and pacemaker input impedance necessary to obtain adequate functioning of demand pacemakers.

Electrogram maximum derivatives (DMAX, SMAX) and electrogram amplitudes (AMAX, UMAX) (Figure 2), were studied in 71 cases during permanent pacemaker treatment. During the acute phase, (at first implantation), 29 patients were studied, and during the chronic phase, (at pulse generator replacement), 42 patients were studied. Of these patients, 27 (acute phase) and 36 (chronic phase) were studied for tissue impedance (RT) and interface impedance (Faraday resistance RF and Helmholtz capacity CH). DMAX and SMAX changed from 3.47 +/- 0.33 V/s (mean +/- SEM) to 2.46 +/- 0.23 V/s and 1.93 +/- 0.20 V/s to 1.32 +/- 0.12 V/s; p < 0.02; p < 0.01. AMAX and UMAX remained nearly unchanged from acute to chronic phase. A paired comparison in 13 patients showed almost identical results. Electrograms recorded in patients with bundle branch block showed no statistical difference in DMAX, SMAX, AMAX, and UMAX compared with electrograms recorded in patients with QRS-complexes of normal duration. No correlation was found between rise in myocardial threshold and fall in DMAX and SMAX from acute to chronic phase; p > 0.8, p > 0.5. Patients with coronary heart disease were found to have significantly higher AMAX than patients classified as having rhythm disturbances of primary cause; p < 0.01. Extremely low values of amplitudes and maximum derivatives were found in some patients with myocardial infarctions and cardiomyopathies. No difference existed in DMAX, SMAX, AMAX, and UMAX recorded from electrodes with a 8 mm2 area compared with a 12 mm2 area (p > 0.5). RT was statistically significantly higher on the smaller compared with the larger surface electrodes (p > 0.005). There was a slight but not statistically significant fall in RT from acute to chronic phase (p > 0.2). RF ranged from 2.0-94.6 kohms. There was no statistically significant differences between the 8 mm2 compared with the 12 mm2 electrodes (p > 0.2). CH varied between 0.7 and 37.0 microfarads, with significantly lower values for the smallest electrodes (p < 0.05). In patients with electrograms of borderline amplitudes and maximum derivatives for being sensed, the low CH found with the small tip electrodes, will gave a higher risk of demand failure if the input impedance in the sensing circuit of a demand pacemaker is too low.

Adult↗
PubMed1978

Patients with high-grade atrioventricular block treated and not treated with a pacemaker.

One-hundred and eighty-one patients with chronic and with intermittent high-grade atrioventricular block (AVB) were studied retrospectively. Seventy-one were treated with fixed-rate, 51 with demand-type pacemaker, 59 were treated conservatively. Observation time was three years minimum and 14.5 years maximum. The mean age was about seven years higher, and 8.7% more patients had chronic AVB in the conservatively treated than in the pacemaker-treated group. About 12% more patients had Adams-Stokes attacks in the pacemaker group than in the conservatively treated group. There were 7% more patients with coronary heart disease (CHD) in the pacemaker group, and 10% more with aortic valve disease among the conservatively treated. Totally 4.4% of the patients had a calcification of the mitral annulus fibrosus. The two groups were comparable as regards functional class (NYHA) and heart size. Survival showed 31% more sudden deaths in the conservatively treated than in the pacemaker group. Sudden deaths were not more frequent among the patients with CHD than in those without. Long-term survival showed the more favourable result for the patients with than without pacemaker treatment. There were eight (11.3%) unexplained sudden deaths among the patients treated with fixed-rate pacemaker, only three (5.9%) among those treated with a demand unit. The fixed-rate and the demand units showed a mean longevity of 37.2 and 34.6 months, respectively.

Age Factors↗
PubMed1977

Haemodynamic long-term effects of metoprolol at rest and during exercise in essential hypertension.

1 Twelve men with untreated essential hypertension in WHO stage I were studied on an outpatient basis to evaluate the haemodynamic long-term effect of a new beta-adrenoceptor blocker, metoprolol. 2 Oxygen consumption, heart rate, cardiac output (Cardiogreen) and intraarterial brachial pressure were recorded at rest in a supine and sitting position and during steady state work at 300, 600 and 900 kpm/min. 3 The subjects were treated with metoprolol (dose 50-250 mg/day) as the sole drug for 1 year and the haemodynamic study was repeated. 4 Mean arterial blood pressure was reduced about 12% at rest and 9% during exercise. The heart rate was decreased about 22% at rest and 20% during exercise. There was no significant compensatory increase in the stroke volume and consequently the cardiac index was reduced about 22% at rest sitting and about 17% during exercise. There was no decrease in total peripheral resistance. 5 No side-effects were seen. 6 The major haemodynamic long-term effects of metoprolol in mild and moderate essential hypertension resemble those seen by other beta-adrenoceptor blockers like alprenolol, atenolol and timolol. The study has not given support to the assumption that metoprolol should cause less depression in cardiac output than other beta-adrenoceptor blockers.

Adult↗