DESCRIPTION

APPARATUS FOR OPERATIONS OF ARTERIAL HEMOSTASIS Technical Field

The present invention relates to an apparatus and instrumentation capable of detecting with accuracy the perforation of a vascular wall and performing the hemostasis thereof.

State of the Art

It is known that in surgery operations which include the perforation of a vessel, for example in coronary diagnostic tests or in angioplasty procedures, a problem arises, at the end of the operation, of occluding the hole in the artery made by the introduction of the catheters used for the operation. At present, several procedures exist to obtain such occlusion, for example by means of biodegradable collgens that are deposited through suitable mechanical devices.

These materials, however, occlude the arterial hole only in a precariuous way, thereby rendering the procedure hardly reliable.

Alternatively, it is known to resort to the traditional suture which, however, implies an invasive and relatively complex operation.

Description of the Invention The object of the invention is to overcome the drawbacks of the prior art .

This object is achieved by providing an apparatus and instrumentation according to the attached claims.

A first advantage is given by the accuracy with which it is possible to locate the region of perforation to be occluded.

A further advantage, related to the possibility of directing cauterizing electrodes to the exact point, is given by the rapidity and efficacy with which the cauterization operates the occlusion.

Moreover, according to the invention, the cauterization procedure can be rendered automatic and, therefore, immediate, by using, as a control element of RF energy activation, the variation of temperature that occurs when the electrode 7 leaves the arterial bed.

The immediacy of the cauterization allows minimizing possible hematic effusions.

The characteristics and advantages of the present invention will be more evident from the indicative, and thus non- limitative, description of one preferred, but nonexclusive, embodiment of invention, as illustrated in the accompanying drawings, wherein:

- Fig. 1 shows schematically an apparatus, according to the invention applied for the hemostasis of an arterial wall; and

- Fig. 2 illustrates a detail of the active electrode of the apparatus of Fig. 1.

- Fig. 3 is a graph showing an example of temperature detection and RF-emission performed by the apparatus of the invention.

With reference to the attached figures, an apparatus 1 according to the invention comprises a hemostasis probe 6 sliding within an introducer or cannula 2 already inserted into the vessel for the test in progress. The cannulla 2 allows introducing the probe 6 thereinside in such a way as to project from the distal end of the body 2, the probe being provided with a temperature sensor 7 located at its distal end and with RF-emitters electrodes 7, 8 disposed at a known distance from the temperature sensor 7.

The electrode 8, which represents the reference electrode of RF-energy delivery, may be replaced by a surgery plate disposed on the back of the patient. In this case, the probe 6 consists of only the temperature-sensing and RF- emitting sensor electrode 7.

Preferably, the same temperature sensor 7 is made up of a thermocouple acting also as an electrode for the local delivery of radio frequency energy able to carry out the cauterization of the perforation 5. To control and activate the electrodes 7 and 8, provision is made for connections 9 and 10 to an external control unit including a radio frequency generator for controlling the power emitted by the electrode 7 and measuring the local temperature induced by the RF-generated heating. According to the invention, the thermocouple 7 is made up of metal connections 11, 12, preferably of copper- constantan combination, welded to the head of the distal electrode and connected to the instrumentation to function also as RF energy-emitting electrode for the local heating of the blood and the cauterizing operation.

The same control unit, therefore, controls the emitting power of electrode 7 during the cauterization of the hole 5 in the artery 4. Once the catheter used for the test under way has been extracted, the probe 6 is introduced into the cannula 2 so that the electrodes 7, 8 result in the arterial bed. Upon starting the generator of the control unit, the electrodes 7, 8 emit a power of 2-3 W and, as a consequence of the thermal flush within the arterial bed, the sensor 7 measures a temperature very close to the basal one. By withdrawing the cannula 2 and probe 6 as one piece, when the sensor 7 reaches the arterial hole, that is, the region 12 around the perforation 5 in which there is a condition of blood' s stagnation, the thermal flush due to the arterial flow is missing, and the measured temperature raises abruptly.

With reference to Fig. 3, the graph in this figure shows how the apparatus position can be detected and, in particular, it shows both the temperature variation measured by the sensor 7 between a region inside the axtery

and the corresponding wall region outside the artery, and the relevant delivered power as a function of time upon the positioning stage.

It should be noted that the produced temperature variation can be advantageously utilized to automatically activate the delivery of power upon the cauterization procedure, preferably but not limitatively, a radio frequency delivery, to obtain the cauterization of the artery hole. It is stressed that the energy delivery for the cauterization is automatically controlled according to the cauterization temperature programmed beforehand (for example at 80/90°) .

Should the delivered power induce excessive temperature, the generator would modulate the delivered power to make it fall within the preset temeperature limits.

In this way there is obtained both an optimal discrimination of the temperature variations, as ensured by the controlled local heating, and a prompt delivery of energy necessary for closing the hole. By way of example, it has been found that a temperature increase δT in the absence of flow is about 8-10 degrees above the basal temperature measured in the artery and, therefore, able to be positively detected by the sensor (Fig. 3) . In this position, the sensor 7 measures therefore an abrupt increase of temperature due to the missed action of "thermal flush".

According to the invention, the extent of the temperature' s sudden rise allows the operator to know that the distal end of probe 6 carrying the cauterizing electrode is at that moment in the region 12 around the hole to be occluded. In the present description, reference has been made to a flow sensor consisting of a temperature sensor that "reads" the temperature difference between a stagnating blood and a flowing blood.

Again according to the invention, it is anyway possible to use different solutions to discriminate the conditions of flow in proximity of the perforation to be occluded. Similarly, the electrodes for the local heating of the blood, and the electrodes for the cauterization of the artery wall, may be replaced by a variety of means, and the same thermal sensor - herein indicated as a thermocouple - could be of a different nature. In particular, the chemical-phisical characteristics of the active electrode are intended to ease the hemostasis process during the delivery of RF energy.

A first characteristic is the choice of a rounded or ellipsoid frusto-conical shape for the distal end of the catheter, in order not to causes traumas to the inner wall of the vessel upon inserting the catheter.

Moreover, in the construction of the active electrodes, it has been found important using materials the composition and working of which are able to minimizing both mechanical and chemical-phisical adhesion of the biological material to the electrode. Among these, electrodes of mechanically polished stainless steel, or of more inert materials, for example ^' noble metals such as platinum and others, may be used. Finally, provision may be made for depositing antifriction substances on the electrode surface which improve the adhesion repellency of the biological material. The invention thus conceived may also be subjected to several modifications and variants, all of them falling within the inventive scope; moreover, all the parts can be replaced by technically equivalent elements.