Historically, both primary and secondary hypertension have been only sporadically diagnosed in domestic dogs, due in large part to the difficulty of diagnosing the condition and the inconsistency in dog’ presenting clinical signs. However, more and more veterinarians are assessing blood pressure levels in their canine patients. As a result, a diagnosis of hypertension is certainly on the increase.
Dogs with primary hypertension usually have normal results on routine blood work, such as a complete blood count and a serum biochemistry profile. Dogs with high blood pressure caused by another underlying disorder, which is called secondary hypertension, may have abnormal blood results that reflect their particular condition; however, these results will not be suggestive of or diagnostic of hypertension. These dogs also may have abnormal results of thoracic radiographs (chest X-rays), abdominal radiographs, ultrasound and/or other laboratory tests based upon their underlying disease processes. Again, those results will not help the veterinarian determine whether or not the animal has high blood pressure.
Hypertension is best diagnosed by obtaining specific, measurable evidence of elevated arterial blood pressure. This can be accomplished in one of two ways. Direct (invasive) blood pressure measurement can be done by inserting a catheter or needle directly into an artery and then using specialized medical instruments referred to as pressure transducers to actually measure the pressure of the blood flowing through that artery. The instruments necessary to perform this procedure are quite expensive. Invasive blood pressure measurement also can be quite uncomfortable for the patient. Direct blood pressure assessment is not commonly performed as a diagnostic technique in veterinary practice today. Nonetheless, it still is thought to be the “gold standard.”
Indirect (noninvasive) blood pressure measurement is quite similar to what most people are familiar with in terms of their own health care. Direct measurement involves applying an inflatable cuff, which typically is placed around a lower limb or the tail of the animal being assessed. The veterinarian or veterinary technician will then hold the limb or tail at or near the level of the heart and measure blood pressure using a mechanical device. Performed correctly, indirect blood pressure measurement is usually quite accurate. It is far and away the most common technique for measuring blood pressure in small animal veterinary practice. Other, more complicated diagnostic techniques may be available in certain veterinary hospitals, including oscillometry and ultrasound Doppler flow.
High blood pressure in dogs is being diagnosed much more frequently these days than it was in the past. However, because hypertension in dogs is almost always secondary to some other medical problem, it is usually most important to diagnose that underlying condition.